i could be wrong, but nothing ive ever read has said that clen has the ability to fight estrogen rebound. you can run clen if youd like, but if i were you id focus on one thing at a time. try to get rid of the gyno with some letro, then once youve succeeded and have that off your mind, youll be nice and set to cut up with some clen. just my opinion. and heres a great read on gyno reversal
http://forums.steroid.com/showthread.php?t=379916
and for your last question, yes its a good idea to run an AI/SERM after letro b/c it brings down estrogen so much that when you come off, you run the risk of it spiking back up. in the link i posted for you it explains what you should do for a letro gyno reversal. good luck