In that case, enjoy! It's a great feeling when you get it working.
If you're going to do it on your synology, see if you need to fix the TUN error. Also, you need to add ip routes to your synology to have the IP's from your VPN on docker forwarded to docker. Make sure these are persistent or added on every startup.
Make sure you allow the VPN to work by adding it to the synology firewall.
You need to setup port forwarding on your router. It needs to point to your synology to the port which is linked to the docker container. You also need to add the route to your router to be able to access your network. For instance, if your VPN has 10.0.3.* and your LAN uses 10.0.0., your LAN/router won't know where to send the response packets to the VPN network. So when connected to your VPN you will never be able to load stuff. If you add that 10.0.3. needs to route to your synology, and your synology knows that range needs to be routed to the Docker VPN container everybody knows where it needs to go.