I have just reread all your posts to remind myself properly of the situation.
OP, of course it's possible he has mental health issues - I mean, choosing to take dirty clothes out of the hamper and put them on, and do it regularly, is not normal behaviour by any stretch of the imagination.
But lets not forget the issues started not just because you wanted him to take on the mental load, but because even when you did take on all the mental load, he was still passive aggressive and lazy. You would ask him to do a task - shopping, cleaning etc. He would agree to that task. He would then NOT do that task. And then, to rub salt into the wound, he would then accuse YOU of being the nag/bitch etc because you wanted to know why the task had not been done.
None of this is the behaviour of a person who has any respect or care for you. And whether or not he also has mental health issues or even if, for example, he has undiagnosed ADHD or a similar but different condition, his responses and behaviour reflect someone who does not care.
And this is on top of him suddenly pulling out the mental health card at a time when the chance of divorce is much much higher, made worse because he isn't actually planning to do anything about this supposed mental health crisis either.
I reiterate that I don't see any reason not to at least consider separation. Get a new lawyer because I also think the chances of him asking or getting 50/50, if you push back, is light (football once a week does NOT count as him taking on 50% of the caring responsibilities) and, if he genuinely believes his mental health is the problem, he can fix that and then you can talk again.