Okay, this guy doesn't seem like the kind you should be hanging around. I mean he's only using you and people who openly use others and admit that that's all they're doing are people that you should avoid. It's not nice to be used and it surely doesn't feel good either so why should you put yourself in that type of situation? That's why take yourself out of that situation by avoiding him. I know that you have a crush on him and that it's hard but with a bit of motivation, I know that you can do it. It's not impossible and it will pay off in the long run.
Concerning how he likes your best friend, tell your best friend about this. As a friend, she should try to understand that you don't feel comfortable about this. If she happens to have feelings for him too, then you two should make an agreement not to bother with him anymore because it's not fair to either of you. But if she refuses to comply with your request, then you'd know that she's probably doesn't really care about your friendship and you should leave her. If she values your friendship, she would at least try to put her friendship first. But keep in mind that sometimes attraction are so strong that they can't help liking each other, so you'll have to make a call on this one.
Well anyway, you sound relatively young so don't worry too much about your crushes right now. You will honestly have plenty of time for that in the future and you'll meet better guys to be with. Just know that right now you should stop flirting with him, avoid him, and move on. As hard as it is to do that, I know that you can do it. Good luck!