Hi, the reason you see HTML is because Auctiva does that behind the scenes, it is "instructions" on how to display the template, what font sizes and colors, and much more.
No, you cannot currently revise listings within Auctiva.
To add the ebay counter, it's in one of the revise tabs in the ebay Revise Your Listing. I can't remember exactly which section its in. But you change it from no counter to the counter of your choice.