Just build a shelf to sit across your tub and set the sump on it with a gravity drain down to the tub, and you should be good to go. Question is, will that skimmer keep up with your bio load for this nice big display?!!!
Looks like you went with a Pan World return pump, good choice!
So, if you don't know how to sheet rock, how did you manage to wrap the sheet rock around that bullnose so perfectly? Looks Great!