Hiya,
Meant to reply to you yesterday evening but left the iPad at work - whoops!
It certainly sounds as if he's coming along very nicely. And I'd say that, from what you say, he seems very happy indeed. Poorly kittens do not run around houses and chase flies exuberantly, even occasionally.
He actually reminds me of one of my old rabbits. She's usually spend her evenings running around the house like a mad thing, up and down the stairs and round all the rooms, with an occasional rest to get her breath back, but once in a while she'd spend the whole time sat in the lounge with us, barely moving. The first time this happened my mum and I got really concerned, and actually thought about taking her to the vet for a check-up, as there was 'obviously' something wrong with her. Luckily my Godfather was there, and he pointed out that she was allowed to rest sometimes! So we let her be, and the next day she was back to tripping us up on the stairs!
Could you give him a late meal of something extra yummy (such as prawns, if he can stomach them) so that he is more likely to eat last thing at night? I'm sure Bobby would approve of this idea too!!!
Tell him I'm glad to hear he's putting on weight, and to keep up the good work of eating all his yummy food!
x