I nearly read the whole thread and there many things which made me think. Having had some issues with my table, Partly because of my own wrong doing, but that is another story. One thing which I would like to mention which may be of help to some, when changing the arm height/VTA, I put index cards (about 7.5x5.5cm) under that thingy that prodrudes out which holds the cue lever and the arm hold. Like a pile so they just fit underneath it.
When ever I loosen that screw on the right hand side of the base the arm can't fall down. If I want to raise the arm I put 1,2 ,3 or how ever many needed on top of the pile. These cards I keep seperate as a reference. To lower I remove a card or two and the arm can gentle sag down. So there is no stress of the arm falling or making issues of fidling to get the right height.