steering issue and im stumped

[dusterbd13]

truck: 1995 c1500 reg cab short bed.
lowered: 5/7
Parts used to lower: DJM lowering spindles (2 inch), DJM lower control arms (2inch) belltech coils (1 inch). rear flip kit, overload leaf removed. has firestone ride right airbags in the back for trailer towing duty. DJM shock extenders.

suspension (other): Bilstein shocks. moog pitman arm, idler arm, inner and outer tie rod ends, idler arm bracket. rockauto complete upper control arm assemblies. ZQ8 cardone steering box. new rag joint. new power steering hoses. old power steering pump of unknown age.

wheels and tires: 1.25 thick front adapters, 1.5 thick rear. 2012 camaro steel 18 inch wheels, 255/55/18 Michelin runflat tires.

aligned to factory spec for the 1995 c1500 (4x now, by 3 different shops)

all suspension components have less than 5,000 miles on them.

problems:
play at center of steering. about 1.5 inch either way from center.
stiff steering (abnormally stiff)
memory steering/wont return to center except manually
very darty/wandering al over the road, requiring extreme attention to stay in the lane, bordering on uncontrollable on narrow roads with sharper turns (45mph posted speed limit, doing 35)

the truck is all but undrivable at this point, and cannot pull the race car. or go to lowes. or go to church. or....

I have been chasing my tail at this point, and feel like I have to be missing something.
in the past 1k of diagnostics, with the truck getting markedly worse, I have:
replaced steering box 3 times
replaced all 4 tie rod ends, pitman arm, center link, idler arm, idler arm bracket, rebuilt rag joint, changed toe, changed tire pressures, changed load bag pressures, greased, and pulled the tie rods and manually worked the spindles to check for ball joint sticking.

im stumped. I haven't made hardly any change at this point in the behavior. ive GOT to be missing something here, but have no idea what. so please, help me out here. my last grasp at this is to think that the ball joints are sticking with the weight of the truck on them, but check fine at droop. but, that seems absolutely preposterous.