Well folks....I dont want to jinx it, but I think I got it.
Took the shaft out again tonight, got a new precision u-joint for the front (which was just replaced, fyi) and marked the location of the slip joint on the shaft.
Took it apart, installed new u-joint, and flipped the slip joint 180. Took for a short 4 mile drive and it feels much smoother. I did this because I called a driveline shop and they said even the slip joint can affect balance if its flipped 180 (never marked it when I installed new joint, took a chance that I installed it backwards, and I think I did).
Its noticeably better, I think I got it. Pretty simple/stupid mistake.
I wont drive it to work for a few days, but when I do I am hoping its solved.