Probably that's right. If there is no plugins in My Account page, the update system will think that's an invalid license key. Have you purchased any premium plugin? What was your email when you bought it?
Hi, you need to use the helper functions to get the fields data and use the JavaScript document.print() to save the web page as a PDF file. Or you can use a PHP library to convert that page to PDF.
Your filter also works. If you want to make it work only on the front end, you need to check with is_admin() function. There is no filters like rwmb_frontend_*.
