APN and MSL settings are relative to cellular connectivity (mobile data), they have nothing to do with WiFi connectivity. The two, cellular and WiFi, are not dependent on each other in any way. A cellular signal being picked up by your phone is completely different than a WiFi signal broadcast from your router, the signals themselves are different and the cellular radio and WiFi radio receiving components inside your phone are separate and different. Stop wasting your time trying to tweak your cellular settings, you could at some point mess up your phone's ability to use mobile data or even make phone calls/text. Whomever told you that was what you should focus on to fix your WiFi issues was misleading you,
You might want to give some thought into hiring someone to come to your home and set things up for you. I had hoped you'd answer my questions as that would make it easier to offer relevant suggestions to the problem but without more info, the problem could be the WiFi chip in your phone, or a just setting up home WiFI network properly in your phone, or how your router is configured, or it could be as simple as powering everything down and restarting.