One thing I will say about the blood will spill blood prophecy. You're thinking a little too much into it about the meaning. I'd say you have to think of the phrase literally. "Blood will spill blood" relates to the fact that Brambleclaw and Hawkfrost shared the same blood. Kin spilled each other's blood. Poorly explained because I simply don't really know how to, but then there's "then the lake will run red". Well Hawkfrost's blood did turn the lake red, I believe. His pool of blood spilled down into the lake {it's been a while since I read that scene} making it red. It's quite literal, but yes, overall a fairly pointless prophecy besides the fact it shaped Brambleclaw's character a little more.
Firestar's character, I will agree, was made a little too perfectly. However, even with good intentions behind everything, he did break the code a few times so those were mistakes. The punishment may not seem like enough in the end and that's perhaps why he kept doing it. Even if Firestar wasn't the one to do all of these, some cat would've and there's no mistake that we'd end up calling the same arguements to them. Unless they didn't get to become leader, then we'd be upset about it. I do have to relate Greywing to Firestar though. Greywing was always the one to do the right things, basically like Firestar, though Grey was forced to leave from the start. Had he not, the series would've been way different. To me, Greywing was like the Firestar of Dawn of the Clans. He had to do good and it always worked out for him, but there were consequences behind everything.