Hi marcpurcell,
Here is your file back. I have put it apart, set all the scale to 1, adjusted all axis/angle, as well as all rotational/target Nulls to z=0 so they are on on “virtual” plane.
After all parts are in they way I wanted to have them, I started to set up a new hierarchy. This is in my understanding how it has to work, following a certain logic. Any change in the hierarchy should be done with a copy, just in case. I hope it “reads well”. :o)
Have a look to the HUD adjustments. You can set keyframes directly there. All other parts are in the Layer Browser. As a little bonus—I have set up the hook/chain so it is always vertical. If you don’t like it, delete the XPresso tag.
I think the slide arm could need some “air”/adjustment, but that is certainly not part of the question ;o)
My best wises for the project