dogs are orally fixated, they use chewing , tearing , ragging, as way of reducing stress, no matter where in or out of the home, free running will tire him physically, but he needs to release stress through biting , watch terriers when they're full of tension, they will get their teeth into anything, branches, clumps of grass, each other, dont matter, when stress builds up it needs to be reduced, orally,,
i would use a tug toy with him in the morning ,10 -15 mins tug play,he might not be interested at first, but tease him with it and he'll get the idea,,best of luck ,,
ALRIGHT FAKER.TH