Ah, that helps. Thanks.
Oddly, even with no udp and using sshuttle, qbittorrent wasn't completely dead in the water. It was uploading a little bit - just dribbles, though.
I'm definitely a network noob, so forgive the question, but if you can set the firewall to redirect TCP packets through a specific forwarded port and then redistribute on the other side (as with sshuttle), why can't you do the same with udp?