I'm a guy and I know guys better than guys know themselves.
I've seen it, been through it and know it. The moment you said they met again for a coffee I knew the deal.
I'm sorry at how negative this is but he's meeting her because hes interested in her. Now I cant say if they've done anything because I dont know either of their personalities but staying up, meeting for coffees, meeting again and being alone at his place I would only assume the worst if I were you and do you know what? I would have every single bloody right to as well.
All this "cant he have a female friend?" bs that also applies to male friends for girls is so patronising. YES. Of course he/she can have friends wtf but "friends" dont meet at apartments alone and drink until 5 in the morning.
The ONLY thing in his favour is he's being honest and telling you he's with her etc. A cheater would probably attempt to hide that but maybe hes just an idiot too who has no clue about what he's actually doing.
Btw all of this applies to females cheating too I'm just sick of it all now. Our society is plagued with dishonesty in relationships these days.
Best of luck and never forget who you are and your value. You can lose him/keep him but you'll always have your value that no one can take away so dont settle for less and that goes to anyone reading this!