yeah, you have it diagnosed pretty well, front heavy and the slack is under the track frame when backing up. you need to find a big counter weight for th eback like a winch. or even fab up a weight box and bolt it on the back and fill with concrete.
i have no idea if it was on d2's or not but some tractors you could change position of the front idlers to high or low position, low for blade work, high for tractor use pulling implements, maybe thy had different diameter idlers you culd get to help keep your arse end on the ground?
that looks like pretty nasty ground your working in, which doesn't help either as the tracks are twisting on the ground a little bit and have less chance to run straight than they would on good hard ground.
You could tighten your track some to help I think. An old joke: old man says" doctor it hurts when I do this," doc says " don't do that". So listen to your machine already!
take that crap off…. its only a d2 and primary designed as a drawbar machine.