for your drain fittings, you need whats called a tank bulkhead fitting.
Lowes and Home Depot doesn't have them, but some plumbing
supplys, and Tractor Supply carry them in 3/4", 1", and 1 1/4" !
Get the 3/4" then get a 3/4"MIP threaded hose bibb at a hardware store.
I think ur looking for' Wolmanized' its not waterproof but it is treated to resisted rot, mold and all that crap. I built my tables in my griw room out of it.