Going back in time wouldn't fix anything. The problem lies in stbx. Don't worry about him. Worry about YOU.
As for him being pissed off, it is convenient for him. So what. It will blow over. The real problem here is that getting D is unpleasant for both sides. You'll both feel like you lost no matter what happens, at least for awhile. Nothing much to do about it except to do as well for yourself as you can.
To that end, stick to business only with him.
And don't stress too much about your recent email exchanges. In the big picture, they are trivial.
