Help! noob in over his head with new ("used") Tenlog TL-D3-pro setup :-(

[curious aardvark]

Sheesh talk about highs and lows.

the bumpy Swingline rubber finger glove I inverted, cut the tip off of, slit lengthwise, wrapped around the cables at the exit from the case and ziptied seem to have firmly prevented any further tugging from pulling on the internal cable connections from the outside

That right there earns you the 'bodger Gold Award for Innovation' :-)

But the head levelling. That's back to the luck.

It sounds like the z-axis end stop might have been too high. Ideally you want the bed - if it has them - with levelling nuts screwed up pretty tight and the z-axis endstop, set as low as you can get away with, so that there is absolutely minimal head adjustment needed.