Hi Jeremy,
I just tried to re-produce this issue on my test portal and was unable to recreate the issue of the email address entered in the Merchant field for the PayPal gateway not being saved but I may not have the exact same configuration as you. Can you login to our test site http://www7.smith-consulting.com/ and try to replicate the error. This will determine if the issue is with the latest version of the cart or an issue with your specific dnn portal/cart install. For login credentials please send an email with a link to this post to kevin@smith-consulting.com
Thanks,