I do know the answer to one of those.
Kingsport doesn't have a monster limit probably to keep consistent with the other expansion boards. Innsmouth likely doesn't have a limit either.
Yeah the Kingsport rift-investigation theme kind of saddens me (how did knocking on a door and finding nobody home help you investigate?). I would have rathered that each location only removes a progress token if you get the right encounters. So sometimes, you won't be able to investigate, even with a random encounter. Clearly some adjustments would have to be made to the frequency of rift progress tokens to make this feasible, but at least the theme would be there.

have way too much free time on your hands. Or something. I for one can't even imagine going through the hassle of separating cards from the decks
. Taking out everything but gate bursts might be an idea.