I got the screws & washers from grainger.com:
Screws (316SS)
Washers (316SS)
I got the 6-32 x 1/4 T-Nuts (18-8SS) from a California-based company called Mesa Fastener, Inc I actually found them by going to this FastenerClearingHouse website and doing a fastener search. I wanted the T-Nuts to be as close to 316SS as possible and PLAIN coated (nearly all of T-Nuts in local hardware stores will be coated with Zinc, which I recommend avoiding)
No. I use a custom insole that has a hard bottom.