Welcome to our forum.
I am sorry to hear about these difficult times you are experiencing. Is there any way to tell why James started acting meaner? Do the three of you talk very often? Sounds like you could use a three-person sit-down (with follow-up discussions).
Ultimately you can't control what they do, you can only control what you do. So talk to them and tell them you want to stay together, at least as a V if not as a triad. Perhaps you could ask them what they'd need to happen, to be able to accept staying together. Whatever their decision is, you'll have to make peace with it somehow.
I hope being on this site will help.
Love means never having to say, "Put down that meat cleaver!"