You are 47 years old. Time to start listening to yourself. Using your own words and own logic, does the following REALLY make any sense?
"Tend to want to be a caretaker for everyone else. Just seeking happiness.". So you took care of your youngest daughter and you "started having conflicts when she turned about 15" and went through "many heartaches.". Doesn't sound like happiness to me.
You "took care of her" again after she was an adult and now she won't speak to you. That doesn't sound very happy either.
"My eldest is my only boy. He and I have always been super close.". I suppose this is why you felt compelled to give him money, free car repair, and free rent when he grew up to become an adult with "several issues.". For all of your caretaking, he is also returning the favor by not speaking with you.
Your middle child chooses not to have much to do with your life (and those in it) because she "never has reason to."
Is your 47 year old brain starting to see a pattern here??
"Caretaking" cannot buy happiness.
If you must take care of something to feel fulfilled, then take care of something that cannot take care of itself (your children are adults and can do this themselves) AND is NOT someone else's. responsibility to take care of (the children of this man of yours). Help an endangered species or volunteer at an animal shelter. Wait! You can't because you work 70 a week?? Then try this: take care of ONLY yourself. You just might find that you are the only one who appreciates your caretaking.