Amber, I'm sorry you're going through all this. There have been too many life changes in too short a time. You're right, you definitely don't need additional stress.
I'm in NO way excusing his current behavior. He had come back and you were trying to work things out. Then this happened. He really stepped it up and helped get you through those first few weeks, which must make what he's doing now harder to accept. I've seen enough with my own and other families in similar situations to know that this doesn't mean he's a bad person.
The stress of dealing with serious illnesses can be overwhelming for everyone involved. During that first crisis adrenaline kicks in.so that we can handle diagnoses and what needs to be done. Initially it brings people closer. Then as things move into the recuperation phase and everyday life is resumed that adrenaline fight response is gone, exhaustion sets in, and emotions are all over the place.
You're still seeing the psychiatrist. She'll have seen every kind of reaction family and partners can have to dealing with their emotions in situations like this. She can probably give you insight to into his actions before, during after the stroke and the MS diagnosis. And she will have access to information and resources that will help you get through this.
I'm glad you have a really good friend to talk to. That's so important. Mumsnet also provides an anonymous place to share.
I'm so sorry for the loss of your father as well.
Sending prayers and good thoughts and wishes your way. 💙