Wireguard runs over UDP, the port is undistinguishable from closed ports for most common port scanning bots. Changing the port will obfuscate the traffic a bit. Even if someone manages to guess the port, they’ll still need to use the right key, otherwise the response is like from a wrong port - no response. Your ISP can still see that it’s Wireguard traffic if they happen to be looking, but can’t decipher the contents.
I would drop containers from the equation and just run Wireguard on the host. When issues arise, you’ll have a hard time identifying the problem when container networking is in the mix.