As long as you can pump the water there and back, it doesn't matter where the unit is placed.
Don't know, Mike. We have two Ultima II 6K's and two upflow J-mat bio-chambers, so all of our bio is wet media; that's one reason we're looking forward to the wet/dry media in the TT/FF. Nitrates, here, are 5-10 ppm out of the tap so water changes, alone, can't get rid of them.
We haven't seen ammonia and nitrite in the pond in almost 4 years now. But we do get some bubbles at the falls, especially when feeding heavily. I'm hoping this unit will solve that problem.