idg - we should be stabilised by 1000' throwing it all out at 4d usually has the engines spooling up with about 100' to spare - our is sop states the the a/c MUST be stabilised with engines above idle at 500' or a GA must be flown. Although with light winds/tailwinds its definately a good idea to drop the gear and flap 3 a little earlier!!
3202b - our company uses the apu bleed to power the packs on takeoff purely to get a better flex temperature - the higher the flex the better as far as engine wear and tear is concerned.