...what I actually think is going on with Dean is this: Dean got back from purgatory and was pretty high...on his own goddamn skills...So shutting the gates of hell was going to be his coup de grace...then suddenly Sam's doing the trials and all the wind is out of Dean's sails. So, of course he wants Sam to tap out and let Dean take over - because Dean was itching for the fight this whole time.

This makes a lot of psychological sense for Dean's character.

...we all only really trust ourselves. Think about when you ask someone else to do something for you? You give them super careful instructions and try to be as thorough as possible...because you aren't inside that persons head.

This is so majorly true! Just like in your perfect example of mailing your sister's package--I have been on both sides of that equation and it is one of the few things that can really make me crazy...

I also think that this is the point where Dean decides that if he can't run this race, then he's going to be the best goddamn support crew that the world has every seen... and seeing as how Sam interprets support and care as babying and not-trusting, this is a slight recipe for disaster.

More than slight disaster :(

You are also spot on in your analysis of Dean's 'you're so hot' response to Portia calling him out--it was an irritating moment, but you do make a valid case for it being in character.

I have to say, this is not an episode I particularly care for, but I like it a lot more looking at it after your evaluation!