MY WIFI SECURITY.

Ok i come here ever now and then hoping I will get the hang of how it works and get some answers. I realize the fault is most likely mine. But I have been having an issue with my wifi for almost a year now. and it gets worse as time gos on.  1st it was just an issue with slow speeds and drops all the time.  Now its progressed to my devices no longer connecting to the 5.0 channel which I know for a fact at least two of them use to.  then suddenly I got devices with odds ip addresses that do not and have never shown on the xfi app. I personal think the app isn't wroth the time. But Xfinity has left me with no other option in some areas.  I have been telling Xfinity for at least 6 mons that my admin tool has security issues. and they tell my is my browser don't worry about it.  Well i ts hard to not worry when u have devices on your network you can not identify and the certificate for your admin tool tells you it dose not match site 

This server could not prove that it is 10.0.0.1; its security certificate is from webui-xb3-cpe-srvr.xcal.tv. This may be caused by a misconfiguration or an attacker intercepting your connection.

Proceed to 10.0.0.1 (unsafe)

I have no idea who or what webui-xb3....... is  maybe my gateway? But   the  .tv has me wondering? I only have  Internet service.  And even if there i s a reasonable  explanation for ALL this. Still why is the certificate not matching? Its all very frustrating. 

thanks for reading hope you know whats going on and can help.