Yes
No its not wrong to be mad at all... it sounds like this guy was seeing if you were interested before dumping his girlfriend, that way if you werent interested he'd still have his girlfriend. cut your losses and move on!!:)
he has a friend that likes you.
I didn't realize that being in a relationship made it illegal to talk to someone from the opposite sex. If this guy is flirting with you, does he do it to everyone? Maybe he is just a flirt. If he is doing it specifically to you either tell him that you are not interested and to stop or tell him to break up with his current girlfriend and start seeing you.
Just accept him as his girlfriend in a polite and sincere way, or if you're not interested just say so BUT gently
Could it be that she is interested in somebody else?
If he likes you, then he won't have the other girlfriend anymore.
It most likely means he wants to sleep with you.
Can you say threesom
Yes, of course he can.
Anything beyond 3 dates I would suspect the guy is at least interested.
ask him
Wheather this guy is giving you signals or not is really your call. But if you determine that he is interested in you, what's the confusion? He has a girlfriend. Stay away. You don't need a love triangle in your life. I'm sure you, like anybody, have enough on your plate. And even if you went ahead and struck up a relationship with this guy, who's to say he wouldn't do the same thing to you? Let him know that if he's interested in you he needs to deal with his current relationship first. If he's really as sweet as you say, he'll respect that.