I was able to answer/address my own questions/issues by (1) Googling "755 permissions"; (2) I modified the "Thank You" template to include a link back to my site. It takes the visitor back to the Home page and if you click on the Contact page from there the form fields are blanked out so this will suffice for now. The Missing Fields page is already set up to get the user back to the form via the Back button so that's fine for now. Later I'll learn how to open smaller more attractive windows but for now what I have is great considering this is my first web site.

Hope this helps someone else! If you follow Steven Priest's tutorial carefully and set the permissions correctly the TFmail script should work fine. Thank you to everyone who helped me with this, including Steven Priest, for writing the tutorial , NMS for making the script available in the first place and Tech Support who let me know about the script and helped me get the permissions set correctly.