It's a balancing game, to take care of how you deal with people and how you deal with yourself.
Truest of true things, ita. And I get the 'I did this for a specific reaction' kind of thing.
And Steph, your description of your dad's behavior made me literally groan in recognition. Just like Sail, I've btdt. So. very. draining.
And I did the same in my situation that she did in hers...changing behaviors in a way that respected the other person as a grown up who could and can take care of themselves. What helped it to not be hard for me is realizing that if I DID do everything 'perfect' (take every phonecall, do an entertaining tap dance, make 'em laugh, make 'em laugh, etc.), the lonely/dysfunction/need would still be there. It's not something that can be fixed from outside the sufferer.
Believe me, if there WAS a way to fix that kind of thing, I'd a) have had a way happier childhood, b) be richer than Oprah right now.
Boundaries are our right and responsibility. Having habits around them that we don't like anymore? Not as hard at it might seem to change.
I'm doing some Rational Emotive Therapy techniques with a coaching client and found "How to refuse to make yourself miserable about anything, yes anything!" by Albert Ellis, the father of RET while waiting at B&N for HBP. It's a quick read with lots of good exercises. If books are at all supportive to you, I recommend this one.