Sounds like a lot of this going on here. Cutting your column and putting a solid joint in is never a good idea. However, you cannot go back to my plunge (OE) coupler without an uncut column shaft. I don't know how you are detecting the lower arm flex, but I recommend the boxing for the torsional load the sway bar puts on it when turning. The strut rods do not act on the lower arm. They aren't meant to pull or push the arm. They are a locator. Alignment sounds good but usually when you max the cams (front all the out, rear all the way in) you are increasing negative camber at the same time. Be careful with too much caster as the more caster, the inside tire wants to lift in turns. Think of a steep rake on a chopper. When it turns it lifts at the same time. There's a limit. I sell Bilsteins as they are a good go to. They are high quality mono tube and last forever.
