This sounds like OCD/compulsive chewing - poor guy. If you have the resources, put him in daycare or somewhere where he can be supervised/corrected for chewing. Look into medication options - find a vet used to these type of nervous/anxiety/OCD cases. Up the exercise and mental stimulation. Biking, running, ball/fetch, tug, hiking, swimming, etc. Tire him out. Enroll in a ob class or start a dog sport - get him occupied mentally so he is less likely to act out on himself. Feed him his meals in an interactive toy (bottle jug, kong, buster cube etc). In the meantime, have him wear a cone when you cannot monitor him.