Starting my first saltwater tank

[Bear44]

Plan
>20G tank FOWLR
>20lb live bahama sand (have)
>10lb eco reefer rock (have)
>10lb live rock/live rock rubble (have)
>Hydor koralia 750
>Aqua Clear 50
>Eheim Jager 150w
>Refractometer (from ebay)
>Coralife salt mix (have)

>2 Ocellaris clownfish

so far i have 1/3 of the equipment, with another 1/3 coming in through mail.

got questions that some of you more experienced people can answer.

1> whats the best salinity level for me? (this tank setup will be FOWLR, no plans for corals/anemones)

2> how deep does the sand bed have to be in order for nitrate consuming bacteria to form?

3> what do you all think of my current aquascape? (possible too much deadspace?)