Anytime I buy a item,I leave positive feedback first because I believe its up to me to let the seller know I'm satisfied with the item,and the transaction. When I sell items I also expect the same from my buyers,because I believe its up to them to let me know first they are completely happy. I learned to do this early on because as a seller leaving feedback first I found that a couple of buyers right after became very rude and demanding,threatening me to pay extra on my part for faster shipping,or for me to pull other auction items they noticed I had for sale and sell it to them directly for cheap in order to make them pleased with the current purchase.
The seller your talking about has a feedback number of 43604. I don't think hes trying to black mail you,because at that high a feedback number yours is pretty meaningless in the large scheme of things. Even if you left him a negative it wont affect his overall percentage.
Also,the only thing I see he really did wrong was send your item late. Sometimes when a seller sales over 3000 items a month mistakes happen,and in the end he shipped your item,and he did keep open communications with you.
As for his payment/feedback instructions,heres mine:
Seller's payment instructions
Please make payment by Paypal only.Paypal only if located outside the USA. My shipping times are between 5-8 working days on average.All used computer items sold as is,but insured by shipping service against damage or loss. Please make payment by 4 days of auction ending or item will be relisted and negative feedback left for not following payment policy.
What he list is pretty normal,and I bet you never thought that he may mostly deal with people in Europe,and seeing your from a NTSC/Canada area may have trew him off too just a tad,so he may have just wanted to make sure your aware you purchased a pal item.
I'd say leave him a positive feedback because after contacting you to make sure you still wanted the item,he sent it. I would just state that the item arrived fine,but arrived very late. If you want to go into better details to explain,you have that follow up option you can do on his feedback.