Ah yeah I wouldn’t be surprised if he has a double NAT going on and needs to put the ISP provided modem into bridge mode.
Perhaps change who’s hosting it? Since you’re in IT you probably have a computer capable of it?
Alternatively you could host a wire guard endpoint have them connect to you that way. But configuring that is a pain on Windows.
Check out the TVs in this article to see if any of them are in your budget.
https://www.rtings.com/tv/reviews/best/by-size/70-75-77-inch