In-law's houses should be treated as they wish. If you have to behave formally in the house(i.e. like a guest rather than family) then know that going in. Act that way, and they will be happy. Act as if you are staying in a snotty bed-and-breakfast or something. Maybe if you tighten up, they will see that it is stiff and formal and loosen up in response.
As for changing stuff in your house, if you don't want it done, then put your foot down and say so. If the in-laws views of raising the kids differ from yours, explain that you respect their views, but YOU are raising YOUR children, and that you would appriciate some respect.
Really aweful in-laws, just darned well avoid them. You are not obliged to be treated badly.
Rant here, rant in other chatrooms, rant of other forums, spend that enregy, so you feel better so you can interact with them calmer. Better to gripe online to friends, then lose it at dear old dad-in-law.
Wolfy