Back end credit card not sending info to PayPal
Lots of questions wrapped together ;)

As for how to test without overriding your account: either use an anonymous windows so you aren't logged in anymore or add manually cid=0 as an extra param should do it

And to avoid any mistake, you might want to install the no-overrite extension that locks the first and last name :
https://civicrm.org/extensions/no-overwrite