So, the odds of a meteorite hitting a 1 square meter area of the Moon are 2.6 x10^-7 (That's about one quarter of a one-in-a-million chance). But, that is per hour.
So, for a year, that is about 2 tenths of a percent for a strike on 1 square meter. Put another way, if you have a a lunar base with an exposed area of 500 square meters, you can expect a strike per year. That is about 10 strikes per year on an area the size of a U.S. regulation football playing field.
That is why I think anything like an inflatable habitat will need local materials formed into shielding.
Regarding astronauts seeing flashes from impact, I would expect them to be more visible from lunar orbit on the dark side. (Not the "far side" but rather the side where the Sun is not currently shining.) I would also expect more actual impacts on the far side than the near side, due to shielding by Earth to some degree.
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