This is long, but please advice?

Your problems seem to happen during those moments you get high together. It is easy to understand he is taking advantage of the situation. He wants what he wants and uses you when your control is compromised. What kind of person confides with you his feelings for another, yet he seduces you? Your former roommate saw through him what you don't seem to recognize, he is not committed. It's okay if you want to keep him as a friend, but you should be aware of his manipulation. You need lay off the booze whenever he comes around.