Q's from a Newbie

[Mindy]

No: HPFGUIDX 23835

Hi, I am a brand newbie here so please forgive me if my q's are 
repeats of already-asked questions.

If Mad Eye Moody was really Barty Crouch Jr. in disguise, why did he 
turn Draco into a ferret at the beginning of GoF? Was he trying to 
pretend to be nice to Harry and on 'his side'?

Speaking of teachers, how come none of them ever got married? And how 
come none of them ever got replaced (besides for the DADA every year) 
by new young graduates from Hogwarts?

Also, is there a school for Witchcraft and Wizardry in the good old 
U.S. of A.? Why only in France and "Bulgaria", out of all places?

And here's a technical question -- not a HP question. How do I change 
the email address where I'd like to receive the digests???