Sorry for the late reply. I’ve been busy all day.
Just one other thought. Have you enabled DMZ on your router? (You shouldn’t use it for this situation.)
If you can, please reboot the Pi and try these commands:
sudo ip route add default via 192.168.1.1 dev eth0 table 22
sudo ip route add 192.168.1.0/24 dev eth0 src 192.168.1.17 table 22
sudo ip rule add from 192.168.1.17 table 22
sudo ip rule add from all to 192.168.1.17 dev eth0 table 22
sudo ip route flush cache
(It’s trying to ensure that traffic that comes in through eth0 also returns through eth0.)
Then try to SSH from outside with (and without) the VPN.