1) Yes. It was a retrofit installed by my LBS, but see below.
2) Yes.
a) Yes.
b) Finger pressure
c) Used a kitchen scale to calibrate finger
3) Allen wrench. The CoMo eccentric tightens by rotating a crankarm against the Allen wrench, as you know. So really very little pressure on the crank.
4) Yes.

So - the nitty gritty. Neither Stoker nor I are big wattage stompers. The LBS adjusted it much too loose. I tightened it to the CoMo spec: 10 lbs. = 1/2" deflection. Part of the install was new BBs and cranks. Riding the bike, it seemed to me that there were greater frictional losses in the system than there were before. I removed the belt and drive chain and spun the cranks. No drag there. I added the chain to the stoker's crank. Some drag there, but little or no difference from my single. I tested the drag on stoker's crank with a postal scale. I reinstalled the belt to the CoMo spec and tested drag again. I was disconcerted to find that the drag had more than doubled. I did notice a variation in belt tension with crank rotation, but it was small. I backed off the belt tension to more like the 10 lbs. = 3/4" that Brad is saying. I found the drag much reduced, so that's what we've been using. I have checked belt tension, but have not found any slackening. Also have not seen any wear on the belt. Also have never slipped a cog. About 1500 miles on the belt.

Source of the drag is a bit of a mystery to me. I can't imagine that small belt tension causing measurable drag on the BB bearings. So it much be internal drag in the belt. But if so, why does lower tension decrease the drag?