Using teflon tape on the primer sounds like a real hassle Breechplug. I think it would be pretty difficult to get the tape to stay in place while inserting the primer, and if you did get it in place you may end up having to pick the tape out of the primer seat between each shot. Let us know how that works for you.

I would not back out the firing pin screw. Backing out the breech plug pushes the primer against the breech face, creating a tight seal.