There is a user kickstart available. You could export the user list, then use that as a template to import new users and their information. Take a look at Kick-Starts and give it a try in your sandbox if you're not comfortable trying it in your production environment.
It was happening to us last week also and I almost opened a ticket, but it seems to be fixed for us now. If it's still happening, keep adding to your ticket!
Not totally understanding your setup, I ran a couple quick tests. I think the custom form that's added to a task to capture your deploy date, only adds that custom information to that specific task. If you add that same custom form to the next task, it doesn't seem to be connected - I can choose two...
Certainly is for me. It's super fustrating, but I now use a password manager, so its shortcuts make if fast to log back in. It's still extremely annoying.
Ours branding was still intact until one day last week when I noticed our branding was replaced with Adobe's. We were migrated back in February, so it took a while before it happened.