I'm sorry you got bullied in college. Are you still going? How much longer do you have? I think it is good to stand up for yourself when you can. Perhaps you could transfer to a new school?

With regard to your father, I would probably let him keep it private. You don't really know what kind of interaction he is having with those women - it could be that they asked him to be friends and he said yes even though he doesn't know them.

I think it's really a good idea to stay as far out of your parent's marriage as possible, personally. It just gets too awkward. I would stop looking at your father's Facebook and try to put that out of your mind as much as you can if I were in your shoes.