Interesting what you say about the last 3 years f150 suspension. Out of curiosity can you share your weight slips. If what you say is true about the last 3 years f150 suspension then all the other half tons would currently make for a better TV. The 3.5 EB is as you say an amazing engine and no other half ton engine compares except for fuel & especially towing economy. But power & personal preferences for brand, comfort, shifter etc are fine I'm not trying to sell you a truck I am trying to help you with your Squirrelly towing handling issues.
I am a fan of air bags for suspension dampening, support & when used in conjunction with a WDH and other weight redistribution. If when setting up your load you used wheel wells measurements etc to get your weight bars set to the best link and used the hitch jack to get the best hitch leverage then that's good but without scale slips it's still eye ball estimates and leaves "the rest of the story" in the dark. Most never learn the how & the why to resolve these or rather weight distribution if that is your issue. To them it just seems like magic that works or doesn't. Many choose to spend big again to get a bigger truck to mask or overcome what they don't want to take the time & apply themselves to understand. Some throw parts at it that can be a solution if they hit the problem. Some believe maybe it was insufficient payload. I believe for many the answer is in the place they don't want to look.