WIBTAH If I told my stepdad off for what he’s doing to my mom and the rest of us?

I, 16f have been living with my mom (46f) full-time for close to five years due to something that happened with my biological dad. Since living with my mom full-time, I’ve seen her date and try things out, but never really work out. my mom has the kindest heart and has probably had the worst luck with men, she’s been cheated on, widowed, and now she’s forcing herself to take care of an alcoholic because she doesn’t see that she’s worthy of more than that. My stepdad (39) has been drinking “since he can remember” and reiterates that anytime anyone asks. That’s his excuse. My problem is, my mom has defended him, supported him, taken him to rehab, and fought off his mom and son multiple times. Micheal has repeatedly stayed in his ways, chosen to cut off his son, and has now chosen to basically walk out on us. Last night him and my mom got into an argument, she gave him the ultimatum that he goes to detox and rehab or when she gets back from her trip the locks are changed. He left and stayed away until she left for work this morning, then came in and passed out on their bed. I saw him this morning and was fuming. him and I have had plenty of conversations about addiction, I personally vape and I’m trying to quit and I also smoke weed, which helps for physical pain. Every time we have this conversation, it goes in circles and anything I say to him goes in one ear and out the other. It’s getting beyond frustrating and I’ve never dealt with this type of alcoholic before. My biological dad is an alcoholic as well, but he’s always been open about it and would just leave the beer bottles in the open. But Micheal hides it and is ashamed and embarrassed, but doesn’t do anything. I can see how badly my mom’s hurting and I know she’s getting upset that it’s starting to affect my sister and I, but I want to know what I can do. As of right now, I’m about to march in their room and tell him off, but my mom said no and she’s a little fragile so I want to respect her. I know I’m a teenager and can’t do THAT much but I know I have a strong head on my shoulders and I want to help my mom.

I’m so sorry this has been so long and thank you if you’ve read this far. I really want to know what I can do

Edit: They’re talking right now. He’s just a drunk blubbery mess. Idek how, he’s been passed out in the same position all day. Boutta start a bet pool w my friends on wether or not he’s gonna walk out again