OP... you sound like you're in a really really tough situation at the moment. I hope you eventually manage to overcome your depression and self-esteem issues. Please look after yourself.
You sound as if you've become a little addicted/ fixated on this guy, and are almost seeing being with him as a solution to everything you're going through. Which isn't good.
I don't know him, and I don't know you, but from everything you've said, he sounds like he just isn't as into you as you are to him. He also, tbh, sounds quite horrible - fair enough if he's not interested in you, but deciding to give things a go with you and then posting a pic of another girl with comments and basically telling you he finds her more attractive than you? That's really hurtful, shallow and just plain rude. No one deserves that. It also sounds like you're making excuses for him - trust me, if he'd wanted to get in contact with you, I'm sure he'd have found a way.
Maybe concentrate on yourself for a bit? Try and work some things out. Focus on your life, your friends, your degree, doing things that make you happy and secure in yourself. Do you have some close, non judgemental friends (preferably not mutual friends with this guy!) who can help you through this and hopefully move on? You say you're looking for closure, but it seems like that by trying to contact him you're just opening old wounds up and making things more painful. Which is probably the last thing you need right now.