It takes a bit of stationkeeping to stay at L2; like keeping a ball at the top of a low, smooth hill - needs a nudge every now and then. More than a circular Moon orbit if you pick your inclination correctly (the Moon is lumpy and not every orbit is stable; look up "frozen orbits").

You're generally correct, but in this particular instance it does actually make sense to call it the dark side. Dark, as in "quiet" from RF interference. Just like some areas on Earth, near radio observatories, are declared "dark" (i.e. everyone tries to avoid using high RF emitting stuff in these regions, even comms satellites avoid it).