Thanks for the thoughts. Here what we came up with:
Got the MAP tested and it showed appropriate voltage at idle. But the voltage did not increase as the RPM increased and pressure changed. So we're thinking a vacuum leak?? I might grab a new sensor to replace it 'just so we know for sure' but we don't really feel it'd be necessary.
Rechecked the MAF and the voltage was 10-11v. We pulled it and cleaned it (though wasn't really dirty) and retried. Voltage was off the charts and bouncing all over the place. So uhhmm,we thinking we broke it worse
This will definitely need to be replaced now.
For the EVAP, I replaced the gas cap with a new one. It really didn't change how the truck ran but we should clear the codes and see if that keeps the EVAP code away. I'm not confident it will.
Under the hood is a rich mixture smell when the truck is running. The fuel filter has been changed prior to Dad ran some Lucas fuel system cleaner through. So, least we know that much.
I'm back home now so can't look at the truck. I'll be down there next week to run a team marathon so I might order those sensors and install them if I can (if I'm not wiped out and I get my pizza and beer to recoup me)
Dad is ready to throw in the towel on the Blazer altogether. I think it can be brought back but it'll need to be torn into a little bit and given some dedicated TLC. He doesn't have much extra time or money to get into it. He's frustrated with it, I don't blame him.