I'll take a shot...
1&2: It prolly won't cause alot of water retention, but it does cause a huge spike in estrogen levels. So prolly no on the water retention, but an anti-e is HIGHLY recommended.
3: There's not a definite time frame or dosage on this, but high doses over a long period of time can cause desentization. For PCT, Dr.J advocates 1000IU MWF for 3 weeks and has never had an issue with desentization.