UPDATE. I ditched VPN Unlimited Wireguard, did another clean install and followed VPNac's Wireguard set up instructions and it WORKED!
https://vpn.ac/knowledgebase/125/WireGuard-on-OpenWRT.html
I need to use VPNUlimited because, unlike VPNac, they regularly change their servers to keep up with TV geo blocks. I will have to contact VPNUlimited support to see what's wrong with their config file.