I have only 5tb external drive that is almost full. Like 50GB left.

That’s just a normal thing storage devices do. Data always ends up adjusting itself to larger storage.

I don’t want a GUI getting between me and my media

Ah, I see, fellow telnet starwarstel.net enjoyer.

I just use tailscale but it’s limited it to three users

Tagging nodes and using auth keys may take care of some of that.