I want to say "yes" but you should still try to change the default ports for any process open to the web. Just because they can't guess your ssh, doesn't mean they can't upload a root php script to your webserver which allows file uploads.
Just be as invisible as possible. Run nmap
on your localhost with the defaults and see if anything is set to open. If so, change that port.
Urgh. I sadly do this all the time
Interactive rebase, amend the commit message for your commit, continue the rebase, and force push.
Thank heavens for Magit which simplifies this process.