What I was referring to is called a Bind Mount, where host directories are exposed to the docker container. You may be fine if it’s an external hard drive. I use bind mounts because they’re easier to back up, but I acknowledge they are less safe.
You may be perfectly fine as you are now. My (and others) suggestions are for added security. As it stands, if there’s no target on your bind, the only bad traffic you’ll get are from bots trying to pick away at your domain and sub domains. Generally they’re not a problem. But being extra safe costs nothing but time.
Show him you’re the bigger person, support him on this happy day, then be on with it. Not going to his wedding would not only make you the enemy. It’d also create hostility and he may be left thinking that your political beliefs drove you away and made you abandon your family. Don’t let some billionaire be the wedge in your relationship with your family.