I smell something and it's not borscht.
Don't give the seller any of your information. DO NOT do that.
If Paypal is legitimately telling you that it won't send money to this seller in Ukraine, that means your money is NOT SAFE going there.
If it were me, I'd ask for a Cancel Order and thank my lucky stars for it.
Don't send the seller a bank transfer. DO NOT do that. I understand this is a more common method of payment in Europe but we're not there and Ukraine is far, far away. It's not as if you can go knock on his door and ask for your money back.
Call ebay to have any feedback and/or Unpaid Item Strike removed if it comes to that.
You'll have to scroll through the menus but it's in Help & Contact at the top of a desktop website page.