No Country for Old Men/Headscratchers

No Country for Old Men

 * So we just established Llewelyn Moss as a man with a fairly poor set of morals...he happens across the aftermath of a bloody shootout, corpses everywhere and a truck bed loaded with drugs, and all he can think about is nabbing the money. The guy doesn't even have the courtesy to close the door of the truck when the dying man asks him to. Also, later in the film, he seems to be a fairly smart and resourceful man (the cat and mouse segments of the movie were intense). So, when he randomly decides to get up, in the middle of the night, to bring a jug of water to the dying man...well, where the hell did that come from? The man was probably already dead, the water wasn't going to safe his life (he'd probably have to take him to a hospital which would bring up a whole new set of issues for him)...fantastic movie but what a ridiculous, out of character lapse in judgement for him to even consider going back.
 * Out of character for a conscience to become overwhelming after several hours? I still, illogically, feel shame over stuff I did in primary school, much less a few hours ago.
 * I'd say the same, this trooper in his humble opinion figures from not just the 1st time he viewed the film but repeat viewing that Moss' morals aren't so poor but in a case of "what can I really do?" (as you pointed out, the man would be dead anyway and taking other options such as getting to the hospital would have brought up more issues, and in hindsight given the events of the movie, might have caused even more damage compared to what we did see). Later on we find out he fought in the Vietnam war, and although we have no real way of knowing just what he went thru, it's all but implied that human suffering and death may not bother him in some ways compared to others (again we have no real way to know so, for all that's shown, me could have been just as apathetic initially before he fought, few things could suggest otherwise). If nothing else, It's not impossible for a person to initially be either apathetic or telling themselves they can just ignore something or decide not to take any action, only to do so later regardless of anything period. It ends up causing the very case of 'No good deed goes unpunished'. It showed he had morals somewhere, and in this case it bit him back hard (him and anyone else who happened to cross his path, intentionally or otherwise). YMMV, but for me, it could be argued as being in character, but again, YMMV, IMHO.
 * Calling the police from a payphone on your way out town would have been more realistic...although less entertaining.
 * Or, maybe Moss just isn't too smart. He's a Vietnam vet whose cunning plan to ambush Chigurh was...sitting upright on a bed in front of a hotel room door, with his gun in his lap. That doesn't just cross the line from Genre Savvy to Too Dumb to Live, it takes a running leap across it naked and on fire screaming yeehaw.

Why doesn't the air cannister run out?
Chigurh uses his cow-braining doohickey fairly regularly throughout the film, so why doesn't the compressed air run out?
 * Those tanks can hold a lot of gas under a lot of pressure, which is why they're so heavy and you see him almost dragging it around most of the time. Since he only uses it less than a dozen times, it would be nowhere near often enough to deplete it during the movie's timespan.
 * Unless I'm misremembering, I can only recall three times he used it onscreen (kills the car driver, breaks the camper's doorlock, breaks the hotel's doorlock and wounds Moss), and then there's the times he probably used it offscreen (Well's hotelroom, entering the building to kill The Man, entering the wife's new house).
 * In addition to how much air the tank can hold, compressed air canisters aren't a particularly exotic item even if they're being used to power one.

Wouldn't people who hired Chigurh have sent...
More people after learning that M***' body was found in hotel w/o the money?
 * Short answer: yes.

Of course, since "the Mexicans" shot it out with Moss before Chigurh ever got there, it might be unclear to "the people who hired Chigurh" who actually had the cash.

BTW, in the book there is a later scene where AC delivers the $$ to the stunned corporate big boss and basically pitches himself for full-time employment instead of contract work.

Chigurh's Blue and Orange Morality is an Informed Ability
It just bugs me that folks in general - and the movie in particular - regard Chigurh as if he follows some sort of moral code "that only he understands." The movie feels like it's affording itself some sort of artistic high horse by telling us, no, Chigurh's not crazy, he just operates under a different set of moral rules than we do (and let's face it, a movie about an implacable man with an oblique philosophy is more interesting than one about an implacable man who just likes to kill people when the coin lands the wrong way). Except we're never given any evidence of this; if your morality is blue or orange, it can still be perfectly rational, though you might have to be an alien or a god or something to comprehend the rationality of it. We're given no justification for Chigurh's actions, either from his own perspective or somebody else's, so we have no reason not to consider him crazy. Plenty of genuinely nutso real-life murderers have thought their actions to be perfectly sensible, seeing logic where there isn't any: that's the definition of insanity.
 * Plus, making up grandiose, narcissistic justifications for your behaviors is an almost textbook sociopath behavior.
 * He is a sociopath, and I don't think that anyone would argue to the contrary. The fact that his behavior fits into the "textbook sociopath" realm adds realism to the movie in This Troper's opinion. However, we clearly see that he follows a moral code that is incomprehensible to normal observers. Having a complex set of rules that only you follow does not mean that you are not mentally ill. In fact, it's probably a warning sign.
 * I don't think anyone is saying Chigurh's not crazy, where have you read that? He's bugfuck insane, no doubt about it. What he's got though, is a very intricate list of justifications for his craziness - he thinks he's an agent of fate, and the people who come across him are simply destined to die. That's a load of crap (as, in the movie, Moss' wife so rightly points out) and if you meet a person like that in real life you either shoot them or run...but it is interesting to read/watch.

Did Sheriff Bell choose to act incompetently to allow Chigurh to escape?
Bell noted that the break-in of the Moss trailer has occurred very recently (condensation on the milk bottle), yet did not investigate by asking the neighbors if they saw anything. The desk clerk would have been able to supply a full description, allowing an APB as Wendell suggested. When Carla Jean gave Bell the location of the motel in El Paso, he did not call the authorities there, but drove to the meeting point himself. Bell knew Llewellyn was being actively hunted, and his decision left Llewellyn exposed for several hours at least. Having seen Chigurh's reflection in the tube at the motel, Bell entered the room without calling for backup. Once inside, he failed to turn on the room lights, leaving plenty of shadows large enough to hide a man. He then walked straight into a brightly lit bathroom, blocking his peripheral vision.

Bell may have simply been following his personal philosophy, expressed at the beginning of the film, "...I don't want to push my chips forward and go out and meet something I don't understand. A man would have to put his soul at hazard. He'd have to say, "O.K., I'll be part of this world."
 * As to your second point, I'll point out that Bell DID give Carla Jean his word that he wouldn't get anybody else involved, in exchange for Llywelen's location.