I think you are all overly optimistic about your fuel savings. You are hoping to save maybe 900 pounds at the very most. Probably closer to 500 in reality.
An axle & springs weighs maybe 200 pounds
2 wheels & tires weigh 150 pounds combined
That is 350 pounds.
What makes you think when towing you are going to save very much?
When thinking about saving 500 pounds, do you see a difference in fuel economy if you have a couple 250 lb guys in the back seat of your tow vehicle?
What do you base your fuel saving numbers on?
I think it is more a matter of wind resistance. Yes, acceleration is a factor but when towing my enclosed trailer, I get just about the same mileage whether my jeep is in it or the trailer is empty.
Yes, balancing is easier with a robust tow vehicle with a weight distributing hitch but still tougher than you think.