"Even if he does transition, those issues will still be there. Different clothes, a different name, application of some cosmetics won't address the root-causes of these feelings. They are just the 'veneer' of womanhood in a sexist society."
^This.
Also,"I don't want people to think he's a pervert, he's disgusting, I'm disgusting for staying with him, people laughing, frowning at us..."
I think many trans people think that saying they are really another sex, will reduce the scrutiny, and in a way it does? People in general seem to feel sympathy at the idea of being "born in the wrong body", in a way they don't at "actually, I hate all the stereotypical male bullshit, mens clothes etc, I much prefer the stereotypically female aesthetic and lifestyle".
I think this is causing all kinds of problems. Imagine if when women first started to wear trousers, society had told them, oh, you must identify as a man, and have medical intervention first, or you'll be ridiculed and possibly attacked.
I hope you and your dh ultimately find support, and peace. And as pp said, don't feel guilty in taking a step back or walking away, if/when it all gets too much, your dc needs at least parent whose mental health is up to the task of parenting, and counselling may open a nasty can of worms, if your theory that he was abused, is true.