This is both good and bad news for me.. I am working on something VERY similar.
One question, you are asking users to pay 7.77NXT (pressumably to a Nxt address you own) for a listing, which is fine and cheap, I assume the client checks to see if the 7.77 Nxt was paid before showing the listing.. but whats to stop people commenting out that one line of code so that it shows all listings whether the fee was paid or not?
Happy to help out with beta testing
Edit: If your FreeMarket system is flexible enough to cater for my needs, perhaps we can join forces so that I can utilize your backend process via an API rather than deploy a 2nd very similar market.