My advice is this. Take your sack and place it in a loose codura or kevlar pouch of some type, something that doesnt puncture. Lather generously with peanut butter. Wave in front of dog and have him gnaw/tug on it.
I'll sit in my recliner and let my dog literally gnaw the livng fuck out of it for about an hour solid while I watch sportscenter after the day's grind.
My sack used to be just like yours but now the fucker is loose as hell. I can jump off the edge of my bed onto the floor with my legs spread and it looks like a fucking flying squirrel gliding through the air.