If it's repeated clicks, that sounds like the starter solenoid...and that sounds like a weak battery. You said you tried with 2 good batteries, and that may be, but also may be that those batteries didn't have the amperage you need to crank.
Try jump starting...and, you should know if you did the cluster test right or not. '120' sound like a possible voltage reading, (it's #9 on cluster), but others might display that also.
I think you'll start with a jump start.
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Mangofy your E46!