Have you used your login for any other TV service? The OTT industry has settled on a pretty broad single sign-on ecosystem. If you've logged into any OTT service with your crendentials, you likely don't need to do it again for any other service.
No. I've got Firefox configured to nuke almost everything on restart, plus I run PrivacyBadger and uBlock Origin. This is not me overlooking an existing login.
(I also run a site-specific browsers via Chrome to isolate my Gmail login and keep Google from knowing who I am, I have no Facebook login, etc. I'm not serious enough to run a VPN or Tor, and my setup isn't enough to guard against browser fingerprinting, but I'm reasonably paranoid.)
Personally it's handy as my ISP lets me watch tv on any device on my home network. They did it badly because it breaks if I change the SSID.
But you're not truly paranoid unless you're using tor or a vpn to get away from your ISP's network. Your efforts mostly are an annoyance to yourself but no impediment to other.
(I also run a site-specific browsers via Chrome to isolate my Gmail login and keep Google from knowing who I am, I have no Facebook login, etc. I'm not serious enough to run a VPN or Tor, and my setup isn't enough to guard against browser fingerprinting, but I'm reasonably paranoid.)