Be disciplined with this! Don't just eyeball it. Measure the distance from your wheel centerline to the fender lip. Measure with stock springs, then measure with the GC's. Don't lower more than about 7/8". The car will settle a bit more, at least another 1/8", as everthing wears in a bit.
1" is a good amount to lower it. Really, don't lower any more than that. It will just hurt your handling.
Why you are installing the struts, I recommend drilling out your upper strut mounting hole a little. I used a 1/2" drill bit. Just open up the hole a bit so that you can get some additional camber. When you reinstall everything, have a friend push in the upper part of the hub to get maximum camber while you are tighening.
Half.
I'm using GC bumpstops on the front. Not a big difference, maybe a little softer. Not required. I like the Truechoice bumpstops.
Yes. DON'T LOWER MORE THAN AN INCH!!
Rob