[gemy]

I'm so happy that physical reasons have been ruled out. Now he just needs to heal from his emotional and mental scarring.
Have you read the training book Nothing in Life is Free?

I have found my Razz to be quite independent and strong willed/stubborn. Very different from my other breed. He can try my patience at times. Also with the unknown history of your rescue, he might have been disciplined harshly on the come command. How I've worked with Razz on the come command, is with a very long retractable lead. That might work for your boy. gradually shorting up the lead until he comes to you.

I wish you all the best, and let us know how you two progress.