The solution is to base it upon the user session timer.

To my understanding, a network switch will relay your MAC address, so it’s sounding like that is what your range extender is. You would need an actual wireless router. You could get a wireless mesh router pair, so you have both a new wifi and range extending. I’d then disable the wifi on your main router. It sounds like they make you use your ISP’s router, but it’s also worth trying to disconnect that and plugging your new router direct into the modem instead to see if you need the ISP router at all. Also, you’d need to whitelist the new device with the ISP.

How do you query the database?