Can you detail us which devices that have LAN and USB ports available? If any of these devices have these connection ports, you could upgrade theses to 5Ghz. You need to migrate as many devices away from 2.4Ghz to 5Ghz as possible as it seems that your area has many other neighboring WiFi routers near by and are probably the main cause of this router dropping WiFi on this radio. I bet that 5Ghz will work way better.
I have this same router and it works great for me however I only have hand full of neighbors near by so channels are not congested.