Unfortunately there is no way to move a villager's house after its already been placed down. Its stupid how you still don't have any control where villagers can put their houses at this point in the series, but that's how it is.
Also, it is possible to get villagers to move back into your town after they've left but you have to have 16 new villagers move in and out before your save forgets Kid Cat ever existed and he can move back in. There is a process of getting villagers to move in and out, but that involves time travel. Its called cycling if you want more information.