I completely agree with your second, third, and fourth paragraphs. No arguments there; those were my thoughts almost exactly. Regarding Bilbo throwing rocks, his choice was a perfect demonstration of our protagonist acting protagonisty, i.e., taking agency in his own fate. I kept thinking, as he and Gandalf walked through the elf army, that given the creatures preparing to attack, being right there in the middle of things was a bad place to be. The likelihood of Bilbo surviving in that location was low.

I liked Legolas running out of arrows, too. In fact, when he first appeared, his quiver didn't look full and I wondered if Jackson was going to use that. I'm glad he did.