Moving the top layer (first 1") typically doesn't disturb much but you still want to avoid moving it around too much since it disturbs your bacterial base. Pouring 1-2 gal
of water into the tank for top off should not disturb your sand if you do it slowly. You should top off every 2-3 days at the most for top off. Your 38 gal
tank should average around 1/2 to 1 gal
a day evaporation at the most.
Caribsea is the same brand I prefer and is pretty good with little rinsing needed IME. Everything should settle down soon.