configure to allow qbittorrent ONLY through VPN

I'm about to pull my hair out. I'm new at working with linux firewalls. I need to set up gufw to allow Qbittorrent to allow connection ONLY through a VPN; essentially providing a kill-switch, should the VPN fail. I've been unable to figure out how to set it up using the simple configuration, and upon searching google, I'm ready to take up a drinking habit. I'm sure it's really simple, and I'll feel really dumb once I finally figure it out, but for now, I need help.

Could someone either list out the steps, or point me in the right direction?

Thank you