Would it be okay to spend the night in the house in 1800s clothing and stay there like it's the 1800s?

I'm sure there would be no problems with that. Wouldn't make a whole lot of sense though as its claim to fame was from the early 1900s and not 1800s.

You could, except you cannot have candles or flames of any kind. But if you wanted to use lanterns and just overlook that you'd be fine. There is also air conditioning in the summer, so autumn might be a good time for that. The bathroom is in the barn, so it would be like going to the outhouse. Sounds kind of fun to me.