I have lots of unescaped ampersands in this form. How can I fix this so I can validate my page as html5
The simple answer would be to go through the add-on code and replace any ampersands with html entities but I'm guessing you've already tried that?
I don't think there will be a quick way to do it other than doing that.
I would say that you really don't need to worry about it. Validation is a guide, not a requirement. Especially at this level. Are you experiencing problems with the forms? If they work, don't worry about it. They will continue to do so until we're all old and grey.