If your using a brand new gasket, especially composite, then you don't need copper spray (but wont hurt to use it). Copper spray is more useful if your going to reuse a metal gasket.

Refreshed? As in cleaned up and reused?

For the price of valves, Id get a brand new set. Along with new guides and seals. Maybe some upgrades springs, and revised lifters

I wouldn't sand the block, lots of junk will fall off the paper, use a wire brush attachment for a drill, polishes to a beauty surface finish.

I believe ARP recommends a higher torque then that, I think its on the instruction paper that comes with the head studs.

As for temps, my new aluminum rad keeps it real cool! Barely ever need the fans, yet its only been about 10C here. So thats something to look into as well.