BRS has a calculator to determine how much sand you would need.
Don't lift the rocks, leave them securely on the bottom. Put the sand in and spread it around. No matter how much you rinse it, you will have a cloudy mess for a day or 2. It won't hurt anything and will clear up. Don't worry about it.
You should use a pretty fine sand, although not that sugar fine stuff, perhaps the next size up. If I had it to do over, I'd get that one that has the small shells in it, but the sand itself is pretty fine. I had some leftover rock that I pulverized and threw in there and lots of seashells and pebbles. My jawfish is constantly building. Put your jawfish house in there as well. He may just use it and you will have less sand getting thrown about. Don't get coarse sand or crushed coral. Too rough. The holes they build are just big enough for them to fit and they are constantly in and out of them....if the sand is too course I imagine they'd get kind of abraded.
I keep my tank 77-78 degrees and the corals and inverts don't seem to mind. Right now the only other fish I have is a purple firefish and he doesn't mind it either. I really enjoy my jawfish. It's a little extra work providing the right environment, but he's a great fish! I'm sure you'll enjoy yours, too.