We noticed the speed doubling as well and thought that might be a way to help the player run away from the townsfolk easier. Might as well use the mechanics that helped me win all those driving games from the late 90s hehe. But very perceptive of you to notice that!
And I agree with your suggestion to add a mark to the discovered houses. I designed the location of every item and enter-able house in the game, and when testing it myself for the 100% perfect ending, I found myself running in circles because I couldn't remember which houses I entered. Having a flag for the houses that would definitely be helpful.
Thank you kindly for your comments and suggestions! :)