You just need to update a few packages Paul.
Quick search will locate a load of guides for you on how to do this, and what to watch out for when doing so. Just backup everything. Also worth clearing out your old images as they soon mount up, then redeploy to your host.
To update packages:
Other guides available just search for 'npm update packages' etc..
To prune all images from the host and do a little house cleaning:
The command you need to run is simply:
docker system prune
After accepting the prune, by hitting 'y', simply re-deploy.
The security audit warnings are quite normal, just run the commands presented. Usually rectifies most audit issues, but again you may wish to update the packages that have issues, also they may not have fixes, depends on the issue.
ALWAYS BACKUP EVERYTHING FIRST!
No biggy, just normal run of the mill Docker stuff. As you add more and more packages you will see this more often mate.
PS... You haven't done anything wrong by the way! 