The Best of Both Worlds

I'm looking for some advice.

1) The fish room will be in the space directly under my stairs. I am planning to drywall it to keep the dust from the furnace room (directly next to it) out. I plan to have glass lids on the two 90's, but not on the skimmer portion of the 30 gallon sump. Do I need to worry about humidity? I can put an air vent into the furnace room if that helps. Not sure if I need some fans to suck the air out.

2) Will the Eheim 1262 be able to handle a 11 foot horizontal push? It's also going up 5 feet and through about 6 x 90 degree elbows.

3) I have 4 drains holes on the external coast to coast overflow box. I was planning to do a beananimal, and use one hole for the return. They are 1" drains. Should I adapt the PVC to 1.25" pipe instead of the standard 1", and have that running to the sump?

Thanks for looking. Drywall is still about 80% done. This will still be a long one.