Welcome to pet talk. I hope we can be of some help.

An 8 mo old lab is a real challenge to anyone, but this poor pup needs TIME with his people and lots of exercise. He is just going crazy being crated all day.

Can you puppy proof ONE room like the kitchen to keep him in during the day using child gates?
Can you let him sleep in your bedroom at night?
You MUST find time to take him for some long walks, or games of fetch DAILY. Do all you can to tire him out.
Can you feed and take him out on a regular schedule?
Can you possibly fence the rest of the yard?
Could you put up a trolley line that he could at least run around on a little?
Can you get him some good stuffable chew toys like a couple of big Kongs that you can fill with dog food moistened with peanut butter? (Get kongs at a pet store)
You say he is not destructive when you are with him...keep him with you as much as possible then.

If you are unable to do most of these things I would really suggest that you find another home for this pup.