Is the Cherokee even going to pull all of that??
I know you have a pretty light Jet Boat, but add on that another trailer/jetski/added drag, that might be a bit much for your rig.
My boat is around 2800-3000lbs, and when I towed it with my Blazer and Jimmy, it did alright, but I knew it was back there, and wouldn't want to tow much more than that. Definately not an added PWC. With my Avalanche it isn't an issue, but that's a LOT bigger truck with a lot more power.