I honestly don't think you need new shackles. The angle isn't going to change with new shackles. Granted, the boomerangs will prevent contact with the bumper, but I doubt that's going to be a problem with a 4" Procomp. More than likely, you'll soon be asking how to get the ride to soften up a bit. Add more weight to the Jeep. That's the only real solution.
I don't run trac bars anymore. Never did in the rear, but only recently did away with the front for good. Honestly, I'd rather have it in there. Steering response is substantially better with a trac bar. What you can do to alleviate some of the slowed response without the trac bar is tighten up the shackles very very tight. But that will decrease ride comfort so it's a trade off. I've just learned to get used driving with fairly poor steering response. It's not horrible, but it sure as hell ain't no sports car.