He knows something is up, and his environment is changing.
Years ago, I had an Akita. He was the PERFECT dog in every sense of the word. Until I packed up to move...he became extremely nervous, showed behavior much like Tucker, and couldn't seem to figure out what he wanted or when he wanted it. He had the only "accident" EVER in his whole life - he marked/sprayed MY SOFA!!!
He was neutered, had never exhibited that behavior in the past, and being an Akita, it was not a tiny spray!!! Took three cleanings and several hundred dollars to finally get the darn thing clean.
Anyway, the two big things I would suggest are:
1) try to keep his routing and his surroundings as unchanged as possible. For example, if you have a spare bedroom with a closet stuffed full, start your cleaning there, NOT in the room where he spends most of his time. Try to keep the changes subtle - clean out drawers and cabinets, but leave all of the knick-knacks and the outward appearance the same as much as possible.
2) When it is time to move, try to dedicate 1-2 days to packing (if you can), and don't pack until the very last minute. Do it all in one fell swoop. I know it's better for you if this can be a gradual process, but having his "stuff" displaced and boxes around will be very unsettling for him.
These things won't eliminate his anxiety, but will make things seem as normal as possible for as long as possible.