Lower control arm parallel to ground - alignment problems?

Sounds like your expectations of "rides nice" are different than mine. I love how mine rides, about the same as my Challenger R/T did and (I expect) any newer Mustang GT. Not knocking your opinion.

In regards to your "always have to drive it" comment, I have an issue with mine where I was only able to get +1 degree of caster on the right and settled for that on both until I get it figured out. So I too have to drive mine when it is a little bumpy or rutted. But I am certain that with more caster it will drive great. Is it possible that your wheels/tires/TB/shocks have nothing to do with how it drives and it is more that you have an alignment that is causing your issue?
I just put offset bushings in mine and can't hit 2* of caster :( was hoping for 4... not sure what the deal is.. MIGHT be too thick of UCA rod bushings pushing it back..