Mate ebay will always back the buyer more than any seller no matter how good or how high your feedback score ,you should however be able to claim for the damage from which ever courier you used as that will be your only hope.

also it does not really matter what text you place in your advert ebay abide by their rules not yours as your terms and conditions are NOT legally binding

also the buyer needs to return the item to you at his expense not yours, then you refund him his full original purchase price not including the return courier fee,and thats going by ebay/paypal rules