I have a 12 Ram 2500 CC LB and tow a 5'er with a 17-1800lb pin. I only sag 2" max. I put Timbrens on. They sit 1" off the axle when empty so when hitched up the rear drops 1"+. They provide a more stable ride. Less body roll.
They didn't improve the ride any just body roll. I've towed with and without them and there' not really much difference. I'm thinking of maybe adding bags next year. I still get some chucking even with the MorRyde king pin. Pin weight is 20% so I know I'm good there. Just not sure if bags will be all that much different. Timbrens are way cheaper and easier to install.
Your pin weight seems kinda low for the trailers loaded weight. You could be getting some chucking from that.