get the kryptons or whatever you said and get these to go in them: http://www.yoursole.com/products/footbeds/softec/ultra/
they give my flat foot an arch which I needed for a good fit, so they should fill in your arch.(I think that was the problem right?)
Yes you should!
What I always tell people when I'm working with them in selecting a boot, is that a proper fitting boot with no adjustments whatsoever should make your foot go a little numb in about a half hour or so. This is before heat molding or anything else is done to the boot.
If you ski in Whistler you'll hopefully be skiing more than just the park so go with the Ghost