Don't know what happened to me that made me this weak.
First, I don't think you're weak. Just beaten down. I understand that. I have been there too, and I can still come across as being weak now. The difference is, I'm not down on myself anymore. I'm strong inside, even when people think I'm being a pushover. So it doesn't bother me when people think that.
Second, you've been in a cult and you've escaped. That shows incredible strength, and in such a short time. So again, give yourself credit where its due. Also taking responsibility for a child not your own, loving her as if she was your own and providing for her as if she was your own - this shows strength of character and responsibility. Again, accept some credit for that.
Third, I don't remember your age, but I think I read that you were in your mid-late twenties? I'll be 35 this year. I never really started gaining confidence after all the criticisms and walking on eggshells until I hit 30. Funny that you mentioned living through your character in your short story. I did the same thing with my first manuscript. My heroine was this kick-ass Captain who got to tell her whole family (mom, aunt, uncle, and of course, HUSBAND) what to do. I gained a huge amount of confidence while writing that book. So I say, keep at the short stories. Its great therapy. (Even though I still say talk to a professional) I also love reading your satires. Keep those up too.
Take care of yourself.