You should be cycled and you should leave the shrimp in till you get fish as an ammonia source.
2" sand bed will be fine and shouldn't become a problem. If you get lots of nassarius snails, they'll stir up the bed. Be wary of fish like engineer goby as they can rearrange rock with their digging. So If you want and big diggers, make sure rock is on glass. It's better to do a deep sand bed in your refugium so if it ever becomes a problem, you can close it off from the display. There's debate on the benefit of a fuge dsb
because if surface area.
As for cleanup crew, the Norms are hermits, turbos, nassarius, astraea starfish, brittle stars. As far as quantities, no hard rule. Build them out as you go because you have a barren tank food wise.
Maybe you start with 6 hermits, 6 nassarius and 3 turbos. Wait on the stars. Remember that turbos bull doze everything so be careful with coral placement.
As for the heat situation. Get 2 300w heaters. One for backup, both in the sump. Nighttime could be a source of fluctuation and one 150 will not cut it for a 150.
To dissipate heat for this MH
's, do you hav a canopy? Fans with the unit? You can always rig a couple of computer fans to blow air across the bulbs.