Firstly why have you waited so long.  You need to act immediately your time is running out , You have been far to leaniant  and should immediately open a Unpaid item dispute to cover yourself.  You can do a mutually agree to end transaction but that also needs to be done immediately but if the buyer wants the item that may not be a good idea. I personally would open a UID ( Unpaid item dispute) which will garrentee you a refund of fee,s and more than likely a sale as the buyer would not want a strke.

It sounds like your buyer knows eBay rules and is trying to bypass the time limit you have on lodging a dispute.

You can and should always unless prior arranged with buyer lodge a UID after a week of not recieving payment you can lodge after 4 days but I always wait a week then contact buyer if a satisfactory reply isnt given I simply just lodge a uid immediately.  You only have 45 days I think from memory to lodge any dispute so do it today to cover yourself.  I think it may have even been changed to 32 days but I cant remember of hand I think 45 days is to leave feedback. But either way your running out of time and need to act NOW.

Lodge the UID today and explain to your buyer you can wait no longer due to ebays time policy which buy the sounds of the way he she is stalling already knows about.  Good luck and come back and let us know how you get on.