So I have been friends with this straight guy ever since starting my course back in September. He is super masc and we've been bros for a good while now. We treat each other like brothers in a lot of ways. I came out to him back in October and he was weirded out by it initially but got over it after a week. Also he's always liked girls and girls have always liked him.
But I have started noticed a few things about him that make me wonder. We've always been open about our sex lives but recently he's started asking me more intimate questions about top/bottoming, BJ's and last week he asked me about rimming and how he's always wanted to try it.
Another thing he does is that when we go to the toilets together/changing rooms, he always takes off his shirt or shows off his abs to me. He's always talking about how ripped he is or his physique in front of me when nobody else is about. Today I needed to have a **** after taking an exam and so he came along with me. When we was in there he kept showing off his abs and talking about how ripped he was.
But the main reason I am really confused is because today me and him was in the library and we was in a really secluded area. He said to me "I bet you could have sex here and nobody would notice" to which I jokingly replied "We should do it

"
I
never say **** like that either, especially to straight guys. It just came out of me. He stared at me and smiled. But the fact that he didn't say "**** off" or "Man that's gay" or something like that made me wonder. I quickly moved on after that.
He doesn't really talk to anyone else in uni aside from me. We have friends but he always looks for me to hang out with. He also dresses impeccably well to the point where it's really flamboyant.
Anyway the point is that I am kind of confused. Can you gays give me some of the classic signs?