1) The usual approach is to do it for the three nights leading up to the full moon, counting the night of the full moon (if it happens at night) or the one immediately before (if the full moon happens in the day) as the third.

2) No, the influence needs to be unfiltered. If you can, put it in an open window on a side of your home that gets plenty of moonlight, but where it'll be sheltered from the rain.

3) That seems extremely busy, but it's something a lot of people have done. At least one Roman emperor had a statue of Jesus on his personal altar, along with those of many other gods...