Why analyse it to this detail. Just let your heart guide you and care as it allows you. If you have a caring heart, you are bound to get hurt. That does not mean you stop taking a chance on people. Just ensure, the people you give your care to, are deserving of your care, or take yourself out of the situation. Otherwise just be yourself, and dont think too much. Let everyone accept you for who you are.
You first have to 'care' for yourself. Sometimes you is the only person who you should really care for. You don't owe anything to anyone. Keep yourself balanced - just enough care - and then you can start looking at 'caring' for others and how much is enough.
YOU must come first.
When you find out share with me.
Oh the enigma!
My mom is this way, and it does cause her deep hurt. She cares way too much for her adult children. She has a dream of owning a horse... but nope, gotta take care of my single-with-kids sister and me... even though we're capable of living with the conditions that we're in just fine...
Caring "enough" means 'where do I draw the line, what's equitable for me and them?' Sometimes, though, the nurturing instinct just doesn't quit... and that makes it difficult for all involved.
I think communication and honesty would help some. If my mom could be reassured in several ways that my sister and I are just fine, then that might help.
Please don't ever let yourself into a position where there's a moderate chance of being hurt. Be good to yourself, also, as well as them. Balance, balance, balance.
Take care, heart of gold.