Boundaries are there to protect YOU, and you need to be able to stick to them.
They will make him angrier, because in a way they prevent him from manipulating you, and force him to own his own stuff.
There are many things you can do in your situation, such as:
- after you planned your trip (and he made different plans to play golf), telling him "We had an agreement to leave at 8am, and that's when I'm leaving with the kids. If you want to play golf and meet us at X later, that's fine, you can get your own way there". Which seems to be what you did. Good!
- if he is spending YOUR money, take away his access to your bank account and CC. You can't FORCE him to spend less, you can't FORCE him to use his money for anything, but your can protect yourself. Give him an allowance if need be.
- setting a boundary for when he is allowed in the house is very difficult. Because the boundary is not about him - it's about you. All you could really do would be to say "if you are in the house when you are not supposed to be, *I* will leave with the kids".
YOU setup the rules for YOUR life, and how YOU will act/behave. He can fit in with those, or not - his choice.
would I help myself by making his dinner and treating him like the child he is? . . . so I can gain his trust and see if he will get treatment?
I don't think BPDs work like that. You can choose to make his dinner, but only do it if YOU want to, not because of anything you expect from him.
You can't force him in to therapy. It sounds like you've been quite clear with him about a number of things. Perhaps putting in boudaries for yourself will make things easier, but if you don't see a future with him, and want a divorce, then that is what you need to do.
SET is about conversation, trying to understand and listen to him.
Do you talk with your kids about his behaviours? Do they know he has BPD? Do they understand what that means?