A lot of people have suggested Tailscale and it's basically the perfect solution to all your requirements.
You keep saying you need ProtonVPN which means you can't use Tailscale, but Tailscale actually supports setting up an exit node which is what you need. Put Protonvpn on the Raspberry Pi, then set it up as an exit node for your tailnet. There's a lot of people talking about how they did this online. It looks like they even have native support for bypassing the manual setup if you use Mullvad.
As long as every client has the ability to use Tailscale (I.e. no weird TVs or anything) this seems like it checks all your boxes. And since everything is E2EE from Tailscale, TLS is redundant and you can just use HTTP.
LLMs are very good at giving what seems like the right answer for the context. Whatever "rationality" jailbreak you did on it is going to bias its answers just as much as any other prompt. If you put in a prompt that talks about the importance of rationality and not being personal, it's only natural that it would then respond that a personal tone is harmful to the user—you basically told it to believe that.