Overtaxed,
Here is my two cents. A weight distributing hitch for what you are doing is going to be a PITA. Reason is after you load it you will have to install the torsion bars on the hitch and how they are adjusted is going to change based on your load. IMO I would not plan on using a WDH with a dump trailer.
I owned a 2004 chevy suburban and towed over the rating of "the vehicle regularly" Now before everyone has a fit hear me out. The hitch and all safety chains where rated for the load. I used a WHD keeping tongue load to within spec. Used a good brake controler and had disc brakes on the trailer. Key here is tongue load, that spec is for the weight on your rear tires. Tow ratings on vehicles change because of drive train engineering specs, driveline rear end ect. that is why you see minor changes year to year. I blew the brake line on the suburban if the brake light on the dash would not have come on you would not have known, as the trailer was doing all the braking.
With that said and based on what I have read of your post. Go with trailer you want forget the WDH load the trailer so that the back of your truck just starts to sag. Watch the loading on the trailer springs and the wheels in the wheel well, that they don't hit, when loaded. If you have to add sides and keep load in the middle of the trailer. Since you are loading same material and driving same route you will figure out what is best. You'll be OK.
Just make sure hitch, ball and safety chains are rated for the max load of the trailer. Get a good brake controler and don't go to fast. keep eye on tire pressure and as long as your careful you will be ok.

That is with WDH I use that same trailer and truck for my skid loader takes everything right to the max. I however go slow and not far, works. The Suburban has been replaced with the truck on the trailer and have purchased larger deck over trailer.
Have dumptrailer that I have pulled behind that suburban we load it as discribed and it worked ok. Suburban didn't like it....... but it worked. That is why we went to the 3/4 ton. My guess is we will have that to the max in less that a year....