Dear brat, don't apologize for the thread, it's good.
I am sorry that so many of us have experienced the other side of the coin, the 'aternative title'. :(
This may not help at all, but it reminds me of something.
In University I ended up in a Sociology (hated it, lol) course, but we read a book on people called the "Ik" (that I remember, lol). Anyway, they were wonderful, kind generous people who 'cared' for and about one another. That is, until their food supply disappeared. Then they became self-serving, angry, hurtful, even violent to one another. They had no word for 'want' (a luxury they didn't have), but about eleven words for 'need'.
The researchers, then, in their 'wisdom' (sic), would give each person 2 cookies a day. One guy (only ONE) would often give one or both away, often to children. Everyone made fun of him, including the children there that he gave them to. Some called him 'mental', no one could understand 'why'. But according to the researchers he seemed the only one not angry, not stealing from others, and at peace. (Actually, they described him as happy). He was silent about it, and didn't respond to the others' (the Ik's) criticisms, or ridicule. Just 'smiled' and continued to do it.
I too, have been co-dependent, I've been altruistic and I've been self-centered. I have done things out of 'duty', or loyalty, but also out of choice.
To me, altruism 'can' exist, because I feel like I've been the recipient.
As far as my own thoughts on it go (solely as regards myself), if it were just a matter of making me 'feel good' (which it often- but not always) does, it would solve ptsd (and SI). But it doesn't.
Perhaps because I know others have not realized my battles, I try to not presume I know theirs'. So if I can 'help' rather than 'hinder', maybe that's a better thing to leave behind in my life, even if I have not left much else, or the actions are very small.
But I don't mean it in terms of (a sense of my own) 'worth', nor is it any motivator to me when people say "there's a 'reward' ", or 'karma'.
More importantly, one thing I do think however, is the only thing ptsd hasn't taken from me is the option to choose what I 'like' (whether that's hot peppers or being so-called altruistic, lol). I can have an 'opinion'. And if I'm lucky I can do what I like, believe what I want, share what I want (at least some times)
.
I suspect if one day ptsd even takes everything (SI), at least until then I can 'choose' (hopefully) to not get entirely bitter- and to keep sharing some cookies. :)