My goodness, you poor thing, that is so hard.
I’m so sorry for your loss - that must be making an already difficult task so much harder.
I’m currently attending a support group for mothers with ASD, and we all find it challenging in very different ways.
I haven’t had the ‘touched out’ problem so much, but I definitely recognise it, and I have on occasion had to tell my DC that I need to have 15 minutes on my own to avoid a meltdown (from me). For me, it’s staying calm when they are suffering from overwhelming emotion that is the biggest challenge. That and getting the three of them to school on time and presentable.
I think the first thing is to acknowledge you are doing something difficult (parenting), that is particularly hard for you (as an autistic mother), in circumstances that most people find hard even to think about (bereavement).
If you feel you’re not doing well enough, recognise first how well you are doing.
Be gentle on yourself.
After that, it’s just a question of reading the parenting books that you find bearable and working out what works for you and your DC (because every family is different and different strategies work well for each).
I like ‘How to Talk So Children Listen’ and ‘Calmer, Easier, Happier Parenting’.