1) You can never post too much! In the SHC manual, there are instances in which too much activity can be a bad thing. Not a single one of them applies to you and none have ever applied to the club. No matter how much you post, there will never be a problem.
2) The White Flute is found on Route 47 in Johto.
3) ARs are acceptable for teleporting to event Pokemon that you could never get otherwise. This includes Mew, Deoxys, and Arceus only - no one else. It applied to Lugia and Ho-oh from 2004-2010, but that law has expired.
4) In any other situation, ARs are not acceptable. For club purposes, you might as well not have one (unless you're going after Mew, Deoxys, or Arceus).
5) The reason for this is that ARing a White Flute gives you an unfair advantage over people who don't have ARs because you'll be able to encounter Pokemon more quickly than they can.
6) Bulbapedia and Serebii can always tell you where to get the items legally. ;)
7) Also, there are Pokemon abilities that increase the encounter rate.
8) Good luck in your hunt!!