Looking for help, or ideas.

If its changing when you are moving the car forward and back, something it not tightened down or something is broke. Typically that situation would be a broken stud hole in the K-member that the lower control arm stud hole goes into. OR the lower control arm stud nut is loose.

What were the "issues" with the old K-member you took out. Whatever happened to it, may have happened to other parts of the car.