Thanks to Chuck I have a new connector to the jumper harness and it starts better than it ever did. However, and I don't think it's necessarily related just coincidental (I think) I have a new, worse problem.
While driving, it will suddenly and randomly start cutting out intermittently, dash lights go on and off, like a studder. If it's bad enough it'll stall. It's like a short or bad ground maybe, though the grounds are solid as far as I can tell. I don't even know where to start looking for this one.
It seems to be worst while driving on side streets, especially coming to an intersection and then taking off.
It seems to pretty stable on the freeway at constant higher speed.
It doesn't do it at idle in my driveway.
All I con figure is that something is being jiggled into a bad continuity.