Spoiler alert...Just assume there will be spoilers in a thread about a show.
Yeah, I dont think the brothers were expecting Hank to have been tipped off. If Hank was unaware he would be dead. If hank hadnt already had the key in the ignition and the car in reverse there is no way he would have gotten the car racing backwards at the brother while being shot at....highly unlikely anyway without the tip off.
As for warning Hank....I think Pollo approved it. I think Pollos felt that the brothers were problematic....not only that, but they were threatening him. They were pressing him and making threats against him on his own territory. Pollos is a clever man...less overt and crude compared to the brothers and the cartel. The old man was right not to trust him, because he is so much smarter and more clever. I think the way Pollos saw it, by allowing them to go after Hank it was a win win situation. It didnt matter if they succeeded or got killed, he would have one problem out of his hair or the other....but maybe he was just a little more pissed off at the brothers and the cartel for bossing him around on his own territory, so he gave Hank the tip-off to even the playing field.
Yeah, I dont think Walt was thinking about Jessie or what he was going through. I think he always thought it was about the money. I dont think Walt had any clue what Jessie was going through after his girlfriend died only to be rejected by his partner, the only thing he thought he was any good at. I think he finally got it and realized that he had to be fair and cut him in....kind of sucks that it happened under a threat, but then again that is how their relationship started....with Walt blackmailing Jessie.