For what its worth - I got started in UniFi when my Asus' wifi got flaky. I turned off the radio and added a UniFi AP (AC-Lite). Problem solved. I just had the AP sitting on top of a bookcase, not even noticeable. It covered my then house at 1700 sq ft. Maybe just adding an AP could improve your situation for now. (In a different house now, I have a complete UniFi setup - including that AC-Lite, which is doing fine!)
You could take a look at the UniFi Dream Router (wifi 6 4x4 MiMo AP built in) or Dream Machine (wifi 5 4x4 MiMo built in) - both are all-in-ones.