1. Yes, but 8 gb is plenty
2. Yes; the board chipset is limited to 1333 as far as I know; I use that chipset with my asus board.
3. No. You can't use ecc ram; use any cl9 9-9-9-24 1.35-1.5v non ecc ddr3 240 pin for best results.
That motherboard can handle up to 16GB of RAM, and you can put that amount in, you just have to buy two 8GB sticks to put in it.
The motherboard supports up to a max of 1333mhz ram, so buying anything faster would be a waste of speed/money.
The motherboard does not support ecc RAM(Error-correcting code memory), so just make sure to buy non-ecc ram.