@Cakelover17 & @MichelleSarn just here to say thank you and send you these too 
@MooseBreath I really wish I could give you and your DH a hug. Sending a virtual one. Please know that if this was your experience with DS, then it must have been really difficult for both of you. It might happen again, it miggt be even harder for a variety of reasons and you need to be prepared for this. However, there is also a very real likelihood that baby no 2 will not be as challenging - a different human being after all, and you guys have already been through a baptism of fire big time. Can I just say big words of praise and well done to both of you. You've taken on loads and dealt with it. DH crumbled under the weight of his illness but still juggled working full time. You've done this. Look how far you've come. I'm nearly tempted to say you can ride anything out now, but I know too well that a MH struggle is real, serious and unpredictable and that it leads to a huge amount of guilt and self-deprecation when you have a tiny baby at home and you're desperate to enjoy them but your brain (temporarily) defeats you. That helplessness is the worst. It sounds to me like your DH would benefit from seeing a private therapist. From experience, MH services on the NHS are on their knees right now, including perinatal MH which might not even be available to your DH anyway. It's seriously bad atm. I wouldn't think much longer about this and go privately. It costs money, but it's so crucial to your family that it needs to be prioritised.
What Athena said above makes a lot of sense too. A separation might be helpful to everyone if you could make it work in practice. Everyone's needs could be addressed more peacefully, with less pressure, and hopefully you would reconcile feeling a lot stronger together.
I think some earlier posts were extremely unkind. A baby, no matter how wanted, is such a major turning point and a shake up that its arrival often leads or contributes to a MH crisis, be it PND, PNA or PNP. Partners' MH can be massively affected too. This is not the reason to dump them because they're unsupportive, on what planet are you on to say something like this? Absolute lack of empathy. If someone is ill, there is only so much that they can cope with. They need to rebuild their MH and they need support. They may end up having another episode or a long term illness, is this in itself the reason to dump them? No. OP's husband is addressing his illness. He's trying to avoid the known and anticipated trigger. Would you say the same about a husband undergoing chemo and unable to care for a newborn like he hoped to? No. His cancer might return, so why not dump him though, would be easier, right? No, it doesn't sound quite right, does it. Yet someone in MH crisis is just not stepping up, a burden, and all sorts of evil. It's so sad to see this attitude.