Does it sound like my best friends boyfriend is gay?

I agree with Davie on this one. First, you guys need to deal with his controlling and nasty ways. Then you can worry about his sexuality. But how you described him doesn't necessarily mean he's gay at all. I know plenty of straight guys that wear the same type of clothing and act the same ways, and they're still straight. You could try and set him up by getting a guy who is gay to talk to him and see if he's flirtatious back. If he is, then there's your answer. If he's completely resistant, or seems uninterested, then it's safe to assume he's not gay.