What is my crush trying to tell me?

You haven't said much about how he behaves with other people compared to you, but in general, if a guy appears to be interested but finds himself tongue-tied with a girl, it's because he's nervous, which is because he's interested. The body language you've described is a definite sign of interest. If you didn't matter to him he wouldn't be nervous, and could be more casual and joke around. So I'd say he's genuinely interested and has no idea what to do about it.