You are awefull close and on the right track, this car has an ignition switch just like any other car and it has very small wires and very poorly designed connectors to and from your ignition, on my car I had to shove some more wire in to get a low enough resistance for the car to turn on. Check under the dash on the column, hunting around you will likely find intermittant wires and connections, like any car it will not be all that fun.
An ohm meter (with extra long leads) going from the destination to the source is helpfull, wire afterall should not have much resistance (you hope)
Another thing is the grounds on this car are always crap, it doesn't hurt for your own future sanity (even if they are good now) to run some small wire back to the battery terminal from each critical ground (aka contactors, solenoid, dash)
Anyway The way this car works is
1. You turn on the ingition
2. The teeny tiny battery (which is many times failed) kicks the solenoid providing DC-DC power to all the 12v components and then the contactor for traction drive.
3. When you press on the gas a final contactor closes to provide traction power to the controller and motor
So to answer your other question the battery err message on the dash means ABSOLUTELY NOTHING. It really doesn't help in troubleshooting or anything else, just means a voltage to the dash is either too low, too high or intermittant or too much resistance somewhere, it mainly errors on 12v problems. My car has always run fine with or without the battery error message, to make it go away requires a lot of work and you may find that one of your modules (which are proprietary and non-purchasable) may be flakey.
So in other words you may want to just bypass the dash and hot wire the contactor through a switch.
Oh and Miles used to sell service manuals
Yahoo! Groups
maybe they still do?
Cheers
Ryan