I'm not sure where or when the delivery estimate of May 7-12 was
displayed, especially since you indicated you shipped Friday (which was
the 7th). If you track on ups.com you'll see the scheduled delivery
date.
Is this what you already did: Go to https://www.ebay.com/ship/prf and
modify " offer carrier specific discounts to buyers. Revising the
listing may not have the rate type change. you may need to start a new
listing.