Thanks Dave & Gil - "counterintuivity" for the win!
Tightening a little did the trick. Am gonna put a tiny bit of anti seize on those threads for the reinstall.
I agree the Jensen tool is of little value - it lasted but the first few seconds of this ordeal.
Ended up making an inelegant tool out of 3/32" fence brace that was snug enough to stay put under load.
Would love it if somebody sold a proper tool for this job (hint, hint)!
-Ted