That's awesome that your Crossfire is running smoothly again!

You're right about the battery voltage, but your battery should be putting out 12.8 volts when the vehicle is turned off. While running, the alternator increases that to the 13.7 - 14.7 volts range (I wasn't sure if you already knew that, I was a bit confused by what "checking the voltage to battery after running" meant). I'd wager cleaning your MAF probably helped more than replacing the battery.

Your engine running rough could've been caused by the misfire DTCs themselves too, I'd be on the lookout for that scenario. ECMs in some vehicles will limit air flow and fuel delivery to prevent damage to the cylinders, but I don't have any experience with misfires in the Crossfire specifically.

I'm replacing my plugs at 100,000 here pretty soon. I don't know how many miles you have, so I can't comment on whether a tune-up is a good idea or not.

Just wanted to throw my two cents out there. I hope your baby keeps on keeping on and the codes don't come back!