you sound like a good guy - sorry you and your family are going through such a tough time. It's really hard when MS changes a person, and of course that will have an effect on your family.
I'd take a slightly different view of the situation. I think it sounds like you and your Mum are bouncing off each other at the moment, and it sounds like there's a lot of latent anger, both in you (at her, for not being supportive, for all the aggro, for being back at home and having to put up with negativity and her criticism) and in her at you - possibly for all the above.
I don't want to be putting words in your mouths. But active MS is hard. Hard emotionally to go through and hard for all those around you. Your Mum could be feeling frustrated with her limitations, her losses due to MS and very scared about the future. Personally speaking I'd find it hard to deal with a child pointing out my emotional lability and my memory problems. It's hard to take, you know what I mean? - hard on your pride and sense of self. She could be scared, angry, frustrated...any of these.
Maybe what I'm saying is for a second, take the MS out of the picture. What if your Mum is upset by all that's going on in the family. If she didn't have MS, and she was critical, pessimistic, angry - how would you handle the situation then? You're back in the family home - never an easy dynamic if you've lived away and return. With no job she could be worried about you, angry with you - I don't know her so I can't say what her feelings are. But I think you need to talk to you Mum, and perhaps with your Dad there too. Perhaps family counselling would help you all.
Yes the behaviour changes can of course be down to MS. I know I don't grasp ideas, situations, concepts etc as quickly as I used to. I have a dreadful memory. But a good 70% of that in my case has been to do with disturbed sleep over a long period of time. MS neurological pain, bladder problems, worries, depression - they all can impact on sleep. Perhaps your Mum is not sleeping well. That can be fairly easily alleviated for her, and that at least might help her outlook on life, her memory, her mood.
Is there an MS support nurse with the neurology unit your Mum attends>? Could, when the tension is a bit lower, you suggest she asks about her memory problems then?
I really hope things get better for all of you, and I really hope you don't mind me throwing in a slightly different view.
RR-MS dx 1998 and Coeliac dx 2003
Copaxone, Cymbalta. EPO, Fish Oils, Vitamin D3 2000 IU daily, Cal/Mag/Zinc, Multivitamin/mineral, Co-Enzyme Q10, Probiotics, Milk Thistle.