And the answer is: Bad Separator
As far as I can tell.
Both sides of the van are holding power just fine.
Removed the separator has connectivity bettween the two power poles.
Connecting power on either side at 12.4v makes it click multiple times and the there is either power on the other terminal or not. I couldn't get any consistent results.
Hitting the "starter" tab with 12v did nothing, whether or not there was power to one of the terminals.
So the question is should I go with another 200A separator or is there a better option?
I can't remember if SMB went from separators to isolaters or vice versa. I know my van was built right at the time they were changing and I figure if I'm going to replace I want to get the better thing... thoughts?