AITA for temporarily blocking and not talking to my mom?

I'll try to make this short, but background info: I'm 23, autistic, ADHD, severe depression, anxiety, CPTSD, and now PTSD. Fiancé is 23. We have a newborn (7 weeks). I have two kids by my ex. We live with my mom, her husband, and my 19yo brother.

I already had a lot of issues and a very difficult time keeping a job. My fiancé lost his job to COVID and couldn't find a new one. My mom and her husband didn't want us staying here permanently, especially with our cats. Finally left and got our shit together.

A week later my son unexpectedly died in his sleep, 3 months ago. He was 18 months old. My fiancé and I found him in his crib the next morning. A little less than two months later, I gave birth to my newborn. So now we're back here because I couldn't stay in the same apartment where my baby died while we slept and couldn't save him. My mom understood.

But her husband really doesn't want us here. He gets on us about EVERYTHING. He tried to make us get rid of our cats, but we already lost two thanks to him and we just lost our baby, we wouldn't get rid of them too. Like I said, I'm ADHD and so is my fiance. We have a hard time with cleaning chores. We try but we forget a lot. We need a lot of reminders. But we try our best, yet we're constantly getting yelled at about something. My fiancé works full time and I stay home taking care of the baby and an autistic 3yo.

My mom started cheating on her husband with her ex husband, aka my step dad and the guy I knew as my dad. She's putting off breaking up with her husband as long as possible because they have a house and a car together. My stepdad was giving her emotional support after my son's death which her husband just couldn't do. But as much as I dislike the guy, cheating is NEVER okay. Plus she's hurting my stepdad. She said once she gets back from her vacation she'll have the talk with him, but right now her husband is under the assumption they might be able to work things out while she's talking about marriage and family and everything else with my stepdad.

It also pisses me off because my 3yo has a strong bond with her husband. This will hurt him when he leaves.

What finally got me though is she refused to help my homeless ex. Not in her backyard, not even in MY car that's parked on the street. His time ran out at the shelter he was in and he had nowhere to go. He gave up all his addictions, got on meds, and is actively applying for jobs and going to interviews to get better for our son. All he needed was a place to stay for one night, but she said it stresses her out too much. She's not even here right now, and it wouldn't be in her house.

I know she's stressed out after my son's death and us living here, but cheating and hurting people plus leaving his dad out on the streets seems like a shitty way to honor my baby who had a beautiful soul.

I'm just so tired and couldn't deal with it anymore. I miss my baby so much plus waking up at night and all my other existing issues...my relationship is hurting from all the stress too. Am I wrong?