I think you should be glad to see your post read so many times, myself I've been in sleep since you posted (I tend to go to sleep pretty early, from your perspective at least). Proper answers may take weeks, you may still need to wait for awhile.
You had pretty good description which should help "diagnosing" the issue. In my opinion everything still points to the rear antenna/amplifier.
I did not look at your wiring, perhaps you could remove the power source to the remote antenna amplifier, at best it could be done from a fuse (unless other critical devices are sourced from the same fuse, then you would need to find the wire).
For the steps to replace the parts I would suggest subscribing to the workshop info service:
http://www.startekinfo.com/StarTek/index.jsp
or buy the service instructions for your car from MBUSA.
