You're being a bit bossy OP. You make it clear what you want to hear and everyone else can fuck off. What gives you the right to order everyone around?
I wonder if you're quite bossy all round in that you seem determined to carve out the relationship you want, regardless what you're using as raw material. Whatever, it's your creation and you won't accept otherwise, despite the overwhelming evidence. Which you snap at people to shut up about becuase you don't. want. to. hear.
I've been on the receiving end of a psychopath and I can attest that they do indeed suck the life and goodness out of everything, like a dementor. They're kind of black. So, even though your story sounds far-fetched, I can see that having one of these life-stealers in your orbit can cause serious damage.
But I just don't buy what your husband has done. I just don't buy it, sorry. He has cheated on you and that's that.
I'm not a psychologist but this was intersting: I spoke to my mum at length, as she dealt with my father's infidelities for many years when I was a child, her view is "put up and shut up", mine is most definitely not . Erm. Er. Well.... well, you are putting up and shutting up. Or you're shutting everyone else up, let's say. You are accepting what he has done and the very strange reasons he uses for doing it. But no, you will have what you want!
If I may just say, without checking the list of acceptable points and unacceptable points one is allowed to make, that, while you are tipping the light fantastic with this high drama, your baby is being treated to the heightened adrenalin and emotion. You say you'll get this sorted by the time the baby comes out (and people have suggested you may want to rethink that - but you knew that already, silly!) as if the baby isn't pretty viable as it is. not going to get into one of those arguments but you need to be calm ffs - the poor thing had to hear that 6-hour marathon.
Please stop getting narked that people 'don't understaaaaaaand'. I think a lot of people do, actually. Please, just move out, move apart, be calm in your pregnancy, take this whole shit down a notch, or ten.