I'm sorry about your mum 💐
I've been through similar with my husband. He's struggled with his mental health for a few years. Throughout it all I've been supportive and taken on far more of the responsibilities of being a parent and generally making sure we live in a decent environment with decent food.
We came out of lockdown to the news that my dad had MND so I spent most of 2020, all of 2021 and most of 2022 helping to care for him, on top of working full time and taking care of the children. He didn't step up once, or offer emotional/physical support. He didn't even stand next to me at the funeral.
I appreciate that everyone has their own problems, but there wasn't an ounce of care/concern/help for me through what is easily the worst thing I've ever had to endure...but I was still expected to support his emotional needs.
Honestly, a year on I'm a fucking mess. I have massive anxiety attacks and am struggling to keep my head above water in work. He could have made a difference, but chose not to even try. I'm not sure I can ever forgive him.
At the moment I'm hanging on because the eldest is at an important time of her education and I cannot afford to live in this area on my wages alone, so I'm putting on my mask and pretending everything is OK for my children. I can't wait to escape. Sadly the youngest will have to deal with leaving her school and friends behind because I can't do this for another 8 years. She'll have time to adjust before big exams though.
Don't accept anything less than what you deserve unless you have no choice. I'm sure being alone and going through what I went through would have been better than going through it with a spouse that didn't care. There's nothing that feels worse than feeling alone when you're laying next to someone who is meant to love you.
Wishing you all the strength and best wishes for your mum to have a dignified and comfortable time with you.