I think you have a yorkie!
My crew have these same behaviors. Play with their toys with their paws, climb up the back of chairs and the couch. We immediately tell them down, and they sulk and come down. Tight spaces as well..... The main concern you should have is the climbing as these guys can "break" easily. Just be consistent in correcting him when he climbs. About the toy....Im not at all sure about this, but is catnip bad for dogs?? Anyways, good luck!!!