This is probably long, I'm sorry

So my dad passed away back in June and since then my mom's mind just seems to be slipping more and more, and my older brother is a deadbeat and no help at all.

For the record my dad was 83, my mom is in her 70's, my brother is in his 30's, and I'm 29yo and living with my mom with no job.

My mom has always been forgetful since as long as I can remember, but since my dad passed she's been forgetting things she's known for YEARS and she's been very emotional too. It's understandable, she just lost her husband and best friend. But just the smallest random thing will set her off sometimes and then she's a crying mess. This is very new, not to mention startling, since literally anything anytime can set her off.

The worst part is though is that whenever my mom gets upset, both now and in the past, she'll talk herself down, like calling herself stupid and useless and on and on. If it were normal circumstances I'd do my best to cheer her up and make her feel better. But when she does this, she talks as though I had called her those things, like I thought she was stupid and useless even though I've never thought that at all! I've told her this too, many many times in fact, but she just doesn't listen to me. I know she's suffering herself, but I hate being treated like I'm the bad guy every time she's upset! Her acting like this when she's upset has happened for as long as I can remember and lately here it's been so often that I'm more frustrated then sympathetic at this point. I'm better with my anger than when I was younger, used to just get angry with her and slam a few doors, but even when I calmly tell her that she's making my feel frustrated/emotional/stressed/etc. and need some time to myself to destress and also give her a chance to unwind, she just gets upset and throws an even bigger tantrum. A literal self-pity party every time. She's never said anything hurtful during these times either, never outright said I was calling her stupid or the cause, but every single time she implies that I'm the one who made her feel so low because she wasn't perfection, and she won't listen to me at all when I tell her that wasn't the case.

I just don't know what to do. It's not like it happens every day but it's often enough that I can't relax. I've already spent a majority of my life struggling with my own anxiety, stress, and depression, with little help or say from my family mind you. But now I have to deal with my mom's current mental state, trying to manage the household since she can't, keeping an eye on my older brother whenever he visits so he doesn't rob us blind, and having to except the fact that I'll probably be stuck at home with my mom, jobless, until one of us croaks.