1. About 37lbs...21lbs per tire(off Bridgstone's site) 16lbs per wheel.
2. Dunno about the tire...but the WHEELS weigh 19lbs each
3. They should work ok, but you might not like the cosmetics because the lugs show with the WRX wheels. Stock acorns can go for cheap around here.
4. There was a change?
Hope this helps!