IMO, you can't over spring a t-bar suspended mopar. However, you can certainly under shock it.

So previously, you stepped from .88 to 1, or a 22% increase. You also went from a 318 to a 440, or another 22% increase. Almost a net zero situation. Taking 50# off the engine for the aluminum bits, you still increased weight 15-17%, so as a percentage, you only realistically stepped up the wheel rate 5%, but you added a rear sway bar and ended up with a slight oversteer. Moving from 1 to 1.12 will step it up another 11% for about a 16% increase in total from where you originally started, so you may put yourself in a slight understeer position relative to where you are at now with the rear sway bar. So you may be able to swap back to the urethane bushings for the rear bar to level things out.

Given the way you like to dial things in, I'd almost wonder if a conversion to a splined tubular sway bar wouldn't be the better choice. Open up the K frame some(its not as strong as you might think) to allow up to 2.5" and pick up the pieces for a splined kit. Odds are you could put on together one for around $200. Swapping out the splined bar for more precise rates could be done for as little as $100, maybe less if you shop for used ones. Plus the options for end links may prevent any potential tire interference issues.