Most Helpful Guy
by the sound of it i think you have your mind made up already, it just seems a case of how to deal with things so you don't hurt him too much.
Most Helpful Girl
You need to put your foot down and explain to him that you will be out if he's not going to commit entirely to you. It's clearly a deal breaker for you to be in limbo like this with him, so you might as well just be honest with him and tell him your concerns. If he doesn't want to commit and actually consider you his girlfriend (no "buts" or "ifs" or "I guess" or "this is my lady friend"), then I see no point in continuing this "relationship" with him.