If compression is going down and rebound is extending the shocks I would stiffen up the front shocks on compression and loosen up the extension some more, probably the same on the rear
Have you check the rear spring rear shackle angles with the suspension unloaded with the wheels off the ground and no weight on the rear tires by having jack stands under the frames yet? If no do that and see what angle you have on the rear shackles
If they hang straight down or are angled towards the front end you need to think about fixing that