Does he state that the shipping discount applies to international customers? If he doesn't, it doesn't. It is much more expensive to ship outside one's own borders.
Is he using the Global Shipping Program?
If he is, he CANNOT combine shipping to international buyers. Another failure of this badly designed program.
If you refuse to pay, he can start Disputes for each of the purchases. However, I understand that only one of them will count as a Strike against your buying account.
If you have no other Strikes for non-payment, this will not affect your ability to bid. (Most sellers have Blocks against bidders with Strikes.)
If you decide the total value of all your purchases with the $11 shipping is worthwhile, you will be able to leave feedback and Detailed Seller Ratings for each of the purchases.
The most effective Feedback is calm and factual. The normal Detailed Seller Rating is Five Stars for a normal friendly transaction. Even Four Stars has a heavy impact on DSRs.