The chains can be "tight" but not transferring any significant load.
That is evidenced by the loss of almost 600lbs on your front axle. It should be the same hitched as unhitched if the WD is doing its job.
Transferring 600lbs back to the front axle of the MH will also alleviate the 600lb overload on the rear axle.
Putting 10-ply tires on half ton trucks since aught-four.