Come on! You knew I'd have to do some (over) thinking.
A couple of things that I've been reading about and wanted to nut out here. I always love reading other people's interpretations on things because, I don't know, it just interests me I suppose.
I've seen quite a variety of interpretations on demon!Dean (I refuse to call him deanmon because I just don't like that mash up). I got the distinct impression that this version of Dean lacked any "real" feelings. I didn't think we saw happiness, sadness or even anger. I didn't feel as though he was having a "good time" because it made him happy. More that it just made him feel good - sating a base need. In the past Dean drank because he was depressed or suffering PTSD, this time I got the feeling that he wasn't trying to suppress any feelings, rather just 'cause he could. It's his version of "howling at the moon". I didn't see an inkling of thought in regard to Sam - only that he just doesn't want to have to deal with him. Same with Anne Marie - no regard to her plight at all. I remember watching and looking for a hint that there's some residual care or remorse from this Dean. But I saw nothing. It was an aspect of Jensen's performance that I really loved (that said, I'm totally open to the idea that Dean does have feelings. The fact that he's avoiding Sam may suggest he knows he'll hurt him if he does and deep down he doesn't want to do that. Or that hurting Anne Marie was a way of deflecting and avoiding feelings he may have for her).
I read an interesting idea that suggested that by Sam ignoring Dean's "Let me go" he's doing much the same as Dean did to him in S9 (and I suppose what Dean did when soulless!Sam begged him not to return his soul). Sam was ready to die in the beginning of S9 but Dean was determined to save him, Dean is ready to (essentially) die and live this new life and Sam is determined to save him. Personally, I'm not convinced because I think the situations are different, but it's an interesting idea. I think it's much more aligned to Dean ignoring soulless!Sam's pleas to remain soulless. Sam won't listen to Dean's pleas either because he knows this is not how Dean would want to live. I'll be curious if they are making a parallel because it will mean that the situation last season will be revisited.
I didn't come across any really good suggestions as to why Cas isn't in the bunker. Just not convenient for the storytelling I suppose.
(spoilery) Carver interview:
I came across this interview
from Carver after 10.01 aired. I always hope he'll give some great insight, instead he just makes it all the more confusing. Aannway, he talks about Sam's shoulder (a bit of a let down) and how the Mark is effecting D!Dean (I can't make out his answer at all. Dean's a demon but the Mark will effect him more if he doesn't feed it. Which mean, he needs to feed the Mark in order for the Mark not to effect him…um…I…what?).
It's also spoilery for a new character (be warned!). And whenever Carver says "It's personal and it's going to pack more of a punch…" I get scared! Maybe we don't want to be constantly punched in the feels. How about tapped lightly on the shoulder - with all the gooey brother feels instead?
Anyway, make of that what you will. I'm not entirely sure he has a clue so I'm taking it with a grain of salt.