As for being selfish, I don't really think you can classify ALL NFs as being selfish. When I had my first job I donated 80% of my paychecks to charity(I was living at home). I always give to the homeless. If someone ever drops anything I am the first person on the ground picking up their item. If I'm ever on the phone(I hate the phone much rather talk in person), I am never talking about myself. I am always stimulating conversation by asking the person about themselves or what's going on with them. I'm much interested in what other people have to say than me speaking about my own thoughts or feelings.
Yes I DID have the stay in a bad relationship syndrome, but I would call it clingyness. The reason I stayed in the relationship is because I knew she would cry and flip and throw a tantrum if I ended it, and I figured at the cost my slight unhappiness, I could bring her joy. Everyone said I was the one getting abused in the relationship and how weird she was, but no way I could try to hurt her.
As for relationships. I have only had 1 real girlfriend because since I can remember, I have always been looking for a girl that I know has potential to be the one I want to marry and spend the rest of my life with. I have no potential to be a cheater, and would always be faithful. I pretty much take everything serious such as kissing and above that. I'm a pretty loyal NF guy.
I never lean on anyone, and I never ask for anything, ever. I don't lean on anyone for emotional stability or friendship. All my friends and co-workers come to me for advice cause I'm usually good with it(sorry not being conceited). It's rarely my going out to tell people about my problems mainly cause I'd feel that most people don't want to hear it(weird).
So I really have no clue what you're talking about. I don't think all NFs are how you described. Maybe they lied.