In your site the price is decided by you why not the buyer and seller decide it. What about escrow way of trading like localbitcoins.com site is having as they have no competition in the P2P market.
The price you see in your account panel is related to bitcoin wallet. its bitcoin price in real-time, by selecting the best price from several exchanges.
Yes but there are many rules in localbitcoins.com. If you have any suggestions please share it with us.