I think some of this is pressure from OW but it also sounds like his talk with the C didn't go the way he wanted. You said she was on board with H leaving the family, not just you. I think she could have called him on some of his BS and that's why the sudden change in D filing.
You said he wanted to use We the People. You could probably give them a call to at least check to see if he can file that way. You do not have to accept his timeline or sign anything that you're not ready to. However, you might want to seek some legal advice because it does sound like very soon you will have to deal with the papers, ready or not.
