AITA for being mad at my family over cat litter duties

Burner account. I (40F) moved back home to live with my mom (70F) after my dad died to help her around the house because she has a chronic sometimes disabling back injury and to get my master's degree. Things haven't worked out the way I planned and I wasn't able to find a job that paid me enough to move out after graduating with my degree. Before I continue, yes, I pay rent monthly, plus $120 a month towards communal cat needs (this doesn't include vet visits, grooming, or prescription food) and I pay my own bills. I've asked to pay my part of the utilities, but my mom won't tell me how much they are and they are all digital accounts so I can't access them. In our rather large house, we have eight cats. I have three cats, my brother (31M) has three cats, and my mom has two. My brother's two male cats are aggressive towards my mom's smallest cat so they are separated. Two of his cats live upstairs with him and one lives in the living room/dining room area with my cats and one of my mom's cats (it's a huge area almost the size of a studio apartment). My male Mainecoon mix is separated from my mom's smallest cat because she is spicy (they sometimes get along) and my male cat does not get along with my brother's youngest male cat (the younger cat caused injuries which required vet trips to two of my cats so my male cat does not tolerate the younger one). In case what I said was confusing our cats are divided by large areas of the house. My three cats, my mom's larger cat, and my brother's oldest male live in the front part of the house. My mom's smallest cat lives in the back part of the house alone with my mom's larger cat getting to come and go freely but the larger cat eats, sleeps, and goes to the bathroom in the front. My brother has his oldest female and youngest male cat upstairs.

I should note until my brother brought home his youngest male we didn't have to separate the cats because I had worked hard to make sure they all got along. My mom was a foster for about a year. We successfully adopted out seven cats before we couldn't afford to foster anymore and the young male was supposed to be number eight, but my brother got attached. We went from three foster fails to four. Two of the foster fails are mine because they were a bonded pair of litter mates and the black one has an eye defect. I knew it would be hard to get her adopted with her sister especially since their prime adoption window was during Halloween and the rescue we worked with banned black cat adoption during October for their safety. So, I adopted them with the intention of moving out soon after graduation.

For a while, my brother and I had the duties divided so that I would feed the cats morning and night while he would clean the cat litter boxes. I want to add that my mom has been obsessed with finding a way to make me clean cat litter since we came up with this arrangement, but we decided on this because my brother wasn't feeding the cats until almost midnight so I ended up feeding them.

A few days ago I got frustrated with my brother for getting defensive about how many towels he had upstairs instead of just bringing them to me so I could wash them. I told him I didn't care how many he had, just bring them down. His response was to tell me to "f" off and hang up the phone. I'll admit I lost it in the car in front of my mom, because I'm very depressed and everyone, especially my family, seems to enjoy seeing how far over the edge they can push me until I have a break down.

My mother's solution to the situation was to take over feeding the cats and I would be responsible for cleaning the front area litter boxes. I told her I would continue feeding my cats because I knew I would end up doing it anyway. If her back hurts, I do the work, and her back hurts all the time. My brother was supposed to take over feeding all of his cats upstairs. It's been two days and I am now feeding seven cats. Except for dry in the morning for my mom's smallest cat and my brother's oldest cat who only eats dry. I am also cleaning the litter for 5 of the cats (my cats plus 1 of my brother's cats and 1 of my mom's cats). My mom and brother each have a cat litter box in their areas so they clean those, but they are only cleaning the litter for the cats that stay in their part of the house, which my male cat isn't allowed into. My female cats are allowed in those parts, but they rarely go into those areas and they ask to go back into their area to use the bathroom. My mom thinks this is fair, but I don't. If I was just feeding and cleaning the litter for my cats I wouldn't be upset. It's the fact that I am taking care of my mom's and brother's cats when they don't do anything for my cats. We keep arguing about it and my mom thinks I should just get over it because I'm being self-centered.

Along with taking care of the cats I am in charge of vacuuming the house (except my brothers rooms), my laundry/my mom's laundry/towels/, cleaning the shower/bathroom, helping with/cooking dinner, picking up orders/grocery shopping, cleaning the cat dishes, cleaning the windows, dusting, helping with trash, cleaning up vomit and poop (not always the cats, but mostly my brother's cats), wiping down the sink/counter, and anything else my mom needs. My mom picks up what she can, does the dishes (I tried taking over but she wouldn't let me), and takes out the trash (she shouldn't but she does). My brother helps me bring in the groceries (does not put them away), brings the large trash containers up the hill so my mom can take out the trash (was his job but he was slow to do it so trash bags were piling up), and lifts things occasionally. My mom claims my brother does other things for her that I don't know about, but she refuses to tell me what those things are. I will admit I have been falling behind in my duties because I am not physically or mentally well. I deal with chronic back and leg pain of my own and other health issues. My brother is the only able-bodied person in the house. If I could afford to move out I would, but I can't. It's my dream to have a home of my own, but things aren't working out that way. So AITA for fighting with my mom and being angry because I think our division of cat duties is unfair?