You are putting yourself and your dogs at risk if he comes back and you dust him with rock salt. What if he doesn't like that little dose of medicine and attacks YOU? That shotgun loaded with salt isn't going to do you OR your dogs any good if things go south during the "education" process.

Take your rifle and your bear tag and dump him. A bullet to the ear is magic and in this case, you definitely need a DRT. BTDT.