I think as far as handling goes, that your comfort and his safety are paramount. If you're worried about his escaping or launching himself too far and getting hurt, why not try handling him when you have a friend over? Then you can do what I do with the girls, let him jump from one of you to the other so he gets his exercise and exploration, but you get to feel comfortable with it.

I've always let them have as much as they'll eat of each food I provide. I have yet to see a sloppy fat crestie, so I'm not too worried about it. Watermelon and strawberry does sound like a nice treat. I should try more fruit variety with my guys, I guess.