Advice on cutting off my narcissistic ex-step dad and uncle?

TL;DR: My family and I finally want to cut contact with my narcissistic ex step-dad and uncle, but it could get very ugly very quickly and get other people involved who don’t need to be. What do we do?

I (24F) have been wanting to cut contact with my ex step-dad (60sM) for 15 years. I will sum it up as shortly as I can, but just in case, I urge you to buckle up for safety reasons. TRIGGER WARNINGS: narcissistic abuse, alcoholism.

We'll refer to my ex step-dad as "R". He married my mom when I was 10, as my bio dad passed away when I was 3. He had been married 3 times previously, never had any bio children of his own. While they were dating, he was very good at convincing us that he was a good man. As my mom later told me, he love bombed us. But I knew something was not right as soon as he pressured me to call him "dad" right after they got married. The next sign was when they got into their first fight that I witnessed (it was shortly after their marriage, but I don't remember the exact age I was). My mom was loading us (me and my brother, 2 years younger than me) up into the car to take us to my grandparents' house, as their fight had gotten ugly. She quickly made us sandwiches for the road, but by the time she was ready I had finished it, and I had written on the plate "I wish I had my real dad back." Was I a dramatic child? Yes, but even then I knew this was not okay.

Fast forward to when I was older, maybe between the ages of 13-18, when I was old enough to really understand the problems of their marriage. I remember shielding my brother from their verbal arguments while I listened in to make sure things did not turn physical. Thankfully they never did, but I learned later that he did shatter her phone by throwing it, and he also threw a water bottle at her that bruised her ear when they were on a trip together. Along with witnessing what he did to my mom, I also remember how he was with me. He was always at a distance, placing himself on the pedestal of fatherhood that he never earned. He was never emotionally involved with me, and he never seemed to care about who I was as a person. He only showed "love" through money. I understand that for a guy this could be very important, but on its own, it means nothing without showing love, respect, care, and everything else that a parent should show. To top it off, he never legally adopted us when he could have, which to me reflected exactly what he thought of us, and yet he expected us to use his last name. 

As I grew older, I also noticed that he partook a lot in drinking. His drinking problems got worse as their marriage deteriorated. He also began abusing marijuana, and picked up a cigar habit. He also had a hoarding problem, which created the byproduct of having a shopping addiction, and from my mom's account she claimed he was in debt several times over the course of their marriage, even though he maintained a job that made him well over 6 figures a year. While we were thankful we had a very nice financial cushion, it came with a price he put on it: dealing with his true self.

I later learned that he has been diagnosed with bipolar disorder and OCD. He was on medication and attempted therapy, but from my observations, he was self medicating on top of these. He never sought true help, and I remember several times him denying that he had any problems and that he didn't need "fixing." While I have sympathy for people who suffer from mental illnesses (I am one of them), it can only go so far when that person does not want to seek help or truly work on themselves. To this day I believe he is still in denial, and he has not accepted accountability for anything he has done.

When I left for college, my contact with him pretty much ceased. He texted me maybe twice a year, and maybe called me once out of the 3 years I was away. Even now, he does not put effort into staying in touch, even after I told him exactly what I need to maintain a relationship with him. Yes, at one point I told him bluntly what I needed, as maybe he was just not capable of knowing that intuitively. Well, it led to no changes.

After the divorce between my mom and ex step-dad (3 years ago), I had hoped she would cut contact with him. Unfortunately, because my mom still needed financial help, he continued to pay for things for her and my brother. I separated as much as I could when I turned 18, and he only pays for my phone bill now through a family plan. I knew that he would use money to keep a hold on my family, and it has worked. My mom saw it as no cost to her, as all he wanted was a text-based friendship out of it, but I recently helped her realize that he always tried crossing boundaries with her. 

Now I'll tell you about my uncle (late 50sM), my mom's brother. We'll call him "C". C has always had a strained relationship with my mom and his mom (my grandmother, we can call "G"). He has been married multiple times, and has had 3 children (2 from his first wife, and 1 from a one night stand he had when he was 18). He neglected to care for one of his children when she had a falling out with her mom after their divorce, so we actually took her in when I was 16. She lived with us for almost 2 years, and we paid for her care and schooling. Since this and another distinct falling out between him and my mom and R, the relationship with him has been almost nonexistent. Without getting into too much detail, he never showed up when tragedy struck the family. He never stepped up to be a son or brother or father to his family, and as an uncle I have lost most of the memories I had with him. My family did have an intervention with him when we finally saw him in person earlier this year (he flew in 2 months after G almost died and we had dropped everything to care for her), but nothing changed. He cried crocodile tears and said he would "do better," and I still have yet to see that. He is also an alcoholic, and I would put him in the category of manipulative narcissist; he knows just what to say to get his way, and according to my mother, he was like this when he was younger as well. 

Recently he has been asking G lots of questions about her husband’s will, her will, and some traveling she is doing. The questions are centered around her finances or assets. Otherwise, he neglects to call her or just be a part of her life. R has also been asking my mom and I questions about money. He has sent me money on multiple occasions without me asking, and unfortunately I have not had the balls l to send it back to him, as I am a young and struggling adult. Knowing that they text on a daily basis (yes, since the divorce they have gotten really close) and visit each other occasionally (they live in different states), I grew suspicious of their behaviors. So I did something I do not do often, and that’s snoop. 

Because of some issue with Apple ICloud, I have had access to R’s text messages for almost 10 years. While it is not healthy for me to be reading his messages, it has helped my family out several times. I caught him cheating multiple times, making extremely frivolous purchases, and lying to my mom or others during their marriage. I never snoop unless I know there's something wrong and it may help my family to know what he was saying.

I was looking at messages between R and C, and discovered they were talking bad about my family. Both of them had insulted each member of my family (me, my mom, G, and even my brother) at least once. C had called us gold diggers essentially, and R agreed. Recently my dog almost lost his life (he’s okay for now), and I spent almost $11k to save him, and R said that he was going to “let ‘me’ figure this one out on ‘my’ own.” While I don’t need his money, I did spend all of my savings that took 10 years to build up, and based on his previous behavior I was honestly hurt that this was the moment he chose to “be a parent” and “let me” figure it out. He also did not show up to help in any way, even though he lives 20 minutes from me. He did, however, message me every day since his incident, which I found very unusual. But the conversations were short, as this man does not know how to maintain conversations. I am very angry that they would even utter my name, as they have no real relationship with me and they know it.

Anyways, after reading these messages, I knew that this was one of the first times they had both admitted how they actually felt about us. After all of the decades we all had tried reconciling with them, helping them, and having connections with them, this is what they thought of us. So, I did tell my mom and G about what I had found. My mom has agreed it’s time to fully separate from them, so I am looking into phone plans and she will be making sure everything is set on her end. G is not sure what to do, as being C’s mom, it is extremely difficult not wanting to try to have a relationship with her son C. I hope she is able to come around for her financial safety, but I understand this is emotionally very hard on her. We have not told anyone else about what we found, as my brother still has semi-good relationships with both of them (he is aware of most of what R has done to my mom). 

However, in order to cut R and C out of our lives, I have researched and understood that we need to completely block them out. As they are both narcissists, it can be predicted that they will both try to cross the boundaries we set if they are not hard. If they are, I expect at least C to get others involved, like my cousins or my brother, to learn more information. It is really important that they don’t succeed in this, so I know that we will need to talk to everyone who may get put in the middle to let them know at least that they should not tell R or C anything if they ask. 

So here’s what I need advice on: How exactly should we go about this? We don’t call or see R and C in person, but texting them about this does not seem right. My initial plan is to cut financial ties to R and ghost him otherwise, but that could not work and also does not seem fair (I at least think he is owed a conversation, but I have no idea where to begin with that). My mom can easily ghost C, but G definitely cannot. I expect C to fire back if he is cut out in any way since he is concerned with G’s will and finances. And, of course, doing any of this leaves my brother in a weird spot, but we do not want to burden him with all of this when he prefers to stay out of things. So what should we do?

If anyone has any questions or clarifying information is needed, please comment and I will respond.