It sounds like a behavioral thing doesn't it? Maybe he is having more trouble adjusting to his new home than it first appeared. I'm sure he is having a wonderful time because kittens can't help but make fun out of everything but maybe deep down he is missing Jan, his dog buddies, and his old home. Hopefully he will settle in and start doing better. I know this has to frustrating for you. I really don't know what else you could possibly do. He hasn't been nuetered yet has he? Maybe he is starting to feel those nasty little boy hormones and he starting to be a little territorial and is marking off his turf.
Sorry I don't have any other ideas but I sure hope it gets better!