Hi Josh,
Maybe you could try skipping going to your mothers this week and see how you feel? Sounds like you're putting a lot of pressure on yourself to go and to 'keep the peace', make her happy etc. I suppose I don't have the full story, such as the reasons why you don't get on with her, but it sounds to me if you think being away from her for your mental health is important it is worth a trial. You'd have to figure out though if you could sit with the feelings afterwards, especially if she tries to guilt you. But remember; you deserve to put yourself first.
Ultimately, it is up to you and how you feel, but I would say it is time to put yourself first and look after your mental health, you deserve that.
Sorry I can't help you with your second question, but I know there are many members here was Aspergers Syndrome who will hopefully see this thread. There's a thread for it too if you want to jump in there, maybe skip to the last few pages, and have a chat about it:
Autisim Spectrum Thread
Welcome to the site, take care