Hi Ian ,
Congrats for the new setup , It's always a great feeling when setting up a new tank,
Let's answer all your doubt above ,
the skimmer you chose is a good one , if can go bigger the better.
As for lights , forget the par38 .. Go for those with more control and better coverage for your tank.
Sump, leave out the rocks and Biohome , skimmer and FR in same compartment. Grow led are good,
Sand in DT ... I saw lots if them @ DE aquatic , live white pink ones
Water , get the LFS to deliver NSW .. Anyway after cycling U gonna change out some water at least 50% , so why waste expensive salts and distilled water.(assuming u don't have a RODI unit)
Next Leave the refuge bare , no sand or soil and put in cheato .If u really want a deep sandbed, put sand into a bucket as deep as u want and put the bucket into the sump. This so it is easy to remove
Oh and run the FR as soon as possible .. Get those that run AIO pallets.
Hope that helped and good luck ..!!