Well, part of the problem is that they deny that my email address is the correct one, even though I still have the PayPal receipt with that address sitting in my archive.
I've dealt with their support team literal hundreds of times. That sounds about right for them. Could it have been possible that you purchased the game on another email, and used the PayPal email to simply pay for the game? Usually they fail to confirm the trans. ID if it's PayPal, but other than that they should be accurate on the original email, so if they say it's wrong, it's probably wrong. Did you get any emails from Mojang to that email in the past, about password resets, unauthorized migration etc?