I know this isn't really what you are asking for, but do you think he is very literal? Maybe it would help to let him know that people see the world more in shades of gray and Santa really wants to know if OVERALL he's been a good or bad boy?
In the second scenario pehaps spending more time with other kids would help (if he's not already) - he could see that they make mistakes too.
A third thought is that you could make a conscious effort to model an appropriate response to mistakes on your part. He probably doesn't notice a lot of your mistakes, but if you point them out and comment on them he might begin to see homw common they are. For example, "Oh, I made a wrong turn. I should have been more careful becasue so and so is waitign for me. I'll go back around and be more careful the rest of hte trip. I'm sure they will understand if we are late. Next time I will map directions...." I'm not suggesting your responses to mistakes are currently INappropriate! Just that he probably doesn't notice them. If you verbalize them all he might.
I remember being in a jury selection pool once and they asked if any of us had ever committed a crime. I raised my hand and went through the entire list of my crimes:
Jaywalking, speeding, put a snowball in a mailbox as a kid (that's a FEDERAL crime, I believe), underage drinking....
It all ended well as I was NOT selected! Seemed like the defense attorney saw me a potentially problematic.
