It's easy enough to cancel your existing listings, just go to your listing summary and there is drop down menu and one of the choices is "End Listing". That will end it and there can be no final value fees without a sale. However if you have chosen extra placement or listing upgrades they may still be payable. If you just listed with the basic free listing (only paying final value fees) you can end them at no cost.
It's best not to start selling here with higher ticket items until you see how the fee structure works. The fees are charged on total cost plus shipping and taxes. As long as you know this ahead you can price accordingly.
I wouldn't advise closing your account immediately, if you take down your listings you can't incur any more costs and it would show good faith (look less sketchy than suddenly vanishing!), especially since it looks like you have had a sale (I don't know how recently). If recent eBay will need you to wait the required time for item to be confirmed as delivered and that there is no issue (30 days from delivery).
