RE: I need some dating advice.
He may still be gun shy because of the last time. The fact that he asked if you were interested in such a roundabout way (via your friend) may mean that he's really rejection phobic too, or just kind of shy.
I can understand your hesitation to ask him out on a date so try taking baby steps. What hints have you dropped? Also, what do you guys talk about? We need details! Did you ever say, after a workout, "I'm dying to get a frappucino. You thirsty?" If not, I'd try something like that. Or, ask him if he's going to working out tomorrow because you wanted to show him some article/book on <insert topic you've previously discussed with him> and wondered what he thought of it. In my experience, a few casual invites and meetings lead to nice dinners together. Good luck and HTH!
Chocolate IS the answer, regardless of the question.