I just moved into a 2200 sq ft house, I initially had the router in the basement so that I could have it connect to the rest of the house. But the coverage was abysmal. I ended up running a second line to the room where I was going to keep the router on the main floor. My basement is unfinished so it wasn't that difficult or expensive. I connected the router to the ONT and then connected the router to the new line back to my basement where I have a switch that connects to the rest of the house.
I agree with what @NFtoBC recommends. For a house that size the Boost WiFi kit is the best solution. Modem should be moved back down to the main panel so you can hard wire all your rooms and a Boost mesh wifi solution will give you great WiFi throughout the whole house if places properly.