What do you do with a puppy that won't behave?

My terrier is 4 months old. We are using the crate training method of house breaking. We've had him 5 weeks and he is not fully housebroken. We take him out for 20 minutes to 1/2 hour 5 times a day and let him run and play in our large yard. We don't bring him in until he pees and poops. He'll poop 3 X a day. Then we bring him in to have some freedom in the house, in a confined room. The minute my back is turned he is into EVERYTHING! He has access to plenty of his own toys and I give him dog biscuits for dessert and 1 dental chew bone a day. Still, he will grab your ankles as you walk by, grab your clothing, shew the furniture, my baskets, unravel my yarn and absolutely anything he can get his teeth into. He still has accidents, and when I try to cuddle with him at night when I watch TV he will only bite my arms and hands. He does this to everyone, not just me. I love my baby even though his behavior is less than desired, but I raised sheepdogs for 20 years and I have no experience with this. I am not afraid of my puppy, he doesn't make me nervous, I continue to establish myself as alpha dog, he's a tiny terror, any advice?