Buyer from hell part 2

Put a post up last week about a buyer that agreed a deal on 2 different items. He made 2 ridiculous low ball offers, I said id accept 1 if he agreed a slightly better price on the other.

He agreed.

Bought the first item at a significant reduction, then refused to pay the more reasonable price for the 2nd. Sent me a tirade of abuse when I pointed out he was reneging on a gentleman's agreement.

Ebay basically not interested, said i can cancel the sale or fulfil it. But if I cancel it then thats a black mark against me and the buyer could leave negative feedback.

So I sent it. Item worth around £300, which i sold for £140. Got an extremely patronising message from rhe buyer about how id learnt a valuable lesson about rhe customer alwqys being read, ending with "thanks for the bargain ;)"

He received it. Immediately raised an "item not as described" request. Photos were a completrly different itwm to what I sent. Ebay advised to accept the refund and if it wasn't the item id sent then he wouldn't get refunded.

Received it back today. It was an item weighing 3 grams, wrapped in more than 700g of heavy duty masking type - inside a shoe box. Took me over 9 minutes to open. Lo amd behold, not the item i'd sent. Same general area, but damaged and worth about £10.

What do i do here? Ive raised it on ebay as "not the item I sent". Am I likely to win?

Ive honestly never dealt with such an utterly awful human being. Absolute scum of the earth.