If you had read her earlier thread, you'd be in no doubt that this relationship was utterly toxic and exhausting and has ruined OP financially (hopefully just for now). It wasn't just one of those "Oh, he didn't put the bins out / admire your new hairdo" LTB scenarios.
WELL DONE OP I know you've really struggled with this for a long time.
As someone who had many years of similarly dramatic/destructive relationships, I have a theory that part of the appeal was that it distracted me from working out what to do with myself. There was no need to work out what I wanted from life, what I enjoyed doing, etc, when there was always a new crisis to deal with. Plus, the rewarding bits (sex, mostly! - but also crazy fun) made it all seem worthwhile... until something else cropped up to remind me it really, really wasn't.
It's the perfect time of year for new resolutions (you don't have to wait for 1 Jan!). What can you cultivate in yourself? You need to find your centre.
Your ex being on the cusp of a new start is a good thing: you can use this to reassure yourself that you needn't worry for her. However, be aware that her life will always be a series of chaotic highs and lows and spectacular crashes, and it is wise to distance yourself. Anyone who does not understand why you need to do so can fuck off. Perhaps they will find out for themselves at some point, when it starts to impact them more directly.
It's not your job to pick up the pieces of someone else's life. You now have a lot of pieces to pick up in your own. Don't get distracted from that.
For some reasons (presumably rooted in childhood), you and I take on responsibility for other people's chaos. There is absolutely no need to do so, but it's hard to override that feeling that someone else's welfare is your primary responsibility. I only managed this by isolating myself completely from the world, and eventually finding someone who looks out for me 100% so I can relax, knowing that having no boundaries is not going to get me into trouble.
You're poured so much loving care into another person's life, and now you must gently turn that focus on yourself. Your own happiness is your real responsibility in life. You've been neglecting that; that's why you feel so uneasy. Make this your goal.
It might sound odd, but for this sort of thing doing Julia Cameron's The Artist's Way can help to locate the stuff that makes us tick.