You two have known each other since you were only 10 years old and he was 16. The age difference is less important now than it was then but let’s remember that this relationship started when you were a child and he was a teen. My guess is that you looked up to him and he thought you were kind of cute. Besides, being hero-worshiped is hard to resist when you’re a 16 year old boy. You two have grown up together, with him always in the position of being older and wiser. Now that you are a young adult, also in college, it doesn’t surprise me that things between you are beginning to change.
Anyone who gets up at the crack of dawn to tutor someone in biology clearly cares for her. But I’m guessing that because of your history his caring is more like big-brother or uncle love than lover love. He does have affection for you. He doesn’t want to hurt you. He probably wants to keep you in his life. But he hasn’t figured out how to change the nature of your relationship to one of loving friendship instead of romance. He’s letting his Facebook give you information he can’t manage to tell you himself. He’s moving on.
What you should do is accept that he loves you like a sister and wish him the best, as a sister would. By all means, keep him as a friend if you can but take the pressure for romance out of it. Then make yourself available to the men in your own school. There is someone out there for you but you have to be open to finding him.
I wish you well.