Opinion on towing and weights

Why is it not achievable or desirable whats wrong with a balanced rig?---

The OP's Durango has an unloaded front/rear weight distribution of about 50/50.
If he adds 700# of people, dogs, and cargo, that load might be distributed about 30/70 due to the Durango's relatively long rear overhang -- giving about 210# added to the front and 490# added to the rear.

A tongue weight of 500# with proper WDH adjustment will result in approximately 0# added to the front axle and 350# added to the rear. This would require a load equal to about 30% of TW (150#) to be transferred to the TT's axles.

The net TV axle load change will be 210+0 = 210# added to the front and 490+350 = 840# added to the rear.
The rear-front difference of 840-210 = 630# is considerably higher than the 150# number which you stated.

To get the rear-front difference down to your 150# value would require a load equal to approximately 50% of TW to be transferred to the TT's axles. And, it would result in about 40% of the TW being carried on the front axle, 10% on the rear axle, and 50% on the TT's axles.

So, I say your 150# differential is not achievable because it would require the WD bars to be considerably overloaded to get a 50% transfer of TW to the TT's axles.

And, I say your 150# differential is not desirable because it also would require increasing the front axle load about 200# above the unhitched value.
The major TV manufacturers and major WDH manufacturers now agree that the front axle load with WD applied should not be greater than the unhitched value, and some specify that only 50% of the removed load should be restored.

Yes, it might be possible for the OP to get the rear-front differential down to 150# -- but not with a properly set up WDH.
Your 150# differential might work in some special cases -- but not in general.

Ron