Should I delete him off facebook for good?

Unfortunately you are learning that all relationships end at some point in time. It's always sad when certain ones end badly and there is always that certain something that went unsaid, for whatever reason. But ultimately the decision is your and yours alone. You can continue to feel sorry for yourself and have those conversations that you saved as a reminder of that sadness or you can delete them and try your hardest to forget about them. Once you get into your university, you'll have a lot of things to do. That is probably going to be your saving grace - you'll be so busy that you won't have time to think about him.