From the picture you've added, it looks like you're missing quotation marks around the NPC name and Vendor tab name. Since you're trying to hard code the names rather than adding them to Character.txt, you should have quotation marks.
As a general point, if you have a problem with implementing anything, challenge any assumptions you make. If you've "added everything correctly" but it still wont work, you have to assume that you must not have added everything correctly!
As for the other points it would be very hard to diagnose without pictures, code snippets or error logs.