This guy is confusing me. Any advice?

The next time he explains how much this girl hurts him say "Honestly, I don't know how good she is for you if she hurts you this much." Tell him your reasons and be completely honest. Let him know the end decision is his, and always let him know you will be there for him when the going gets rough. If the stay together, try and be really supportive. If he breaks things off with her, subtly let him know you still have feelings for him. Hopefully things will fall into their right place. Good luck!