I think Darryl is taking the loss of Sophia the HARDEST of the group, and that's why he was so reactive to Lori's stupid comments.
As for the walkers in the barn, the people feeding them chickens didn't stick around long, and you and I watching those scenes didn't see a dead girl walker in there either. Remember, we're talking what a week since the walkers were put in the barn? They may not have even fed them every day.
As for the scene in the bar, no, the guy putting the gun down was NOT trying to defuse the situation, and Rick knew it. The guy climbed over the bar, providing him a bit of cover, and put Rick between himself and the fat guy with the shotgun. Rick knew he was being put between two shooters and was expecting one to open fire at any time. I can't actually tell WHO seemed to start to draw first, has anyone stepped through the scene to see? But I have no doubt the guy behind the bar would have fired first if he thought he would win, and Rick did to. He did the right thing putting them down, and now Herschel will know how much luckier they are at the farm that it was Rick and his group that came by first.
(oh crap, back to a Han vs Greedo argument too)