Have you done any research on which antibiotics Nautella sp. may be particularly susceptible to? Have you thought about seeding your tank with bacteria from a healthy tank right after antibiotic treatment?
I had a lot of water in my crawl space at one point. Sump/frag tank/150 gallon Rubbermaid, this was a huge problem to keep temp. I think a big factor is how big your sump will be under your house relative to your display.
HOB filters are not likely to cut it for a fish only or a reef aquarium. It may be best to drain the tank get an overflow box and plumb in a sump, look into live rock, and a protein skimmer as well. What type of lighting do you have on the tank? Also make sure the tank is cycled before adding...
I honestly have not tested N or P for a couple of years. I do have and think the regular trident works well. I do have a spare trident in box in case my trident ever goes down though. I have not needed it though.
I'm updating all my outlets to have a ground right now in a place we just got. Electrician is charging about 150 per outlet including all labor and materials. Some areas walls will have to be opened up and patched. No knob and tube just no ground.
Put one of these in if you can find one. Looks like the replacement is not as good as the old model. https://www.supplyhouse.com/Panasonic-FV-04VE1-WhisperComfort-40-20-or-20-10-CFM-Ceiling-Spot-Energy-Recovery-Ventilator?srsltid=AfmBOor9uwtKWMyRQXS-eZDW5AdiF6YEyxOz2TJGvGWwpNmvgoTvZBBr