1. My reaction was pretty much complete surprise. As for an explanation, I think that's why this book gets 4 stars instead of 5. I don't like that it was never brought up again, that's a pretty HUGE implication to just leave alone. No motive is contemplated, no sub-plot is ever made past this book. It seems like just a lazy plot twist to give Ax a real reason to question his loyalties. Once that was accomplished, there was no reason to ever write about it again, which is too bad. Perhaps one explanation is the extremely war-weary were trying to force an Andalite loss to force the Andalites into negotiation for a peaceful solution.
2. Really, all it takes is a similar goal. If the goal is significant enough, people will work together despite differences and challenges. I think it is portrayed reasonably well in this book.
3. I always really liked the portrayal of the Andalite military in all the books. Ruthlessly efficient and dedicated to their goal, no matter the cost (which isn't a good thing.) I think that the Andalites can grudgingly respect and learn from the successes of others, but in the end, if they don't fit in the plan they don't fit in the plan. The Andalites saw an opportunity to win, at the cost of earth, and they didn't want to risk their plans for a 'primitive' race.
4. I really think that is part of what made this book good, it had a history attached that was previous in the series which gave it depth. I really liked the re-occurence (even if the plot to set it up kind of smelled of deus ex machina.) It tied up some loose ends and people got to read the way in which the Animorphs helped the rest of the universe. I would have liked to see more continuity to the series, I think the ending books suffered severely for lack of it.
5. I really liked the Leeran race, the concept behind a completely psychic race is really interesting, and I think the individuals that were portrayed were portrayed well for a race that would have that ability. Though, since they were amphibious, I don't know why the Animorphs didn't use it more. Stand behind a wall, psychically read Visser three, get all the future plans, and win. I think they were rather under-utilized as a morph.
6. I think Ax handled it realistically for Ax. Throughout the series his biggest vice was pride in his people, and the betrayal sent him into a complete mental and emotional tailspin. I think it also touches on a lesser spoken about weakness of Ax, his complete lack of trust in his own intuition. (Or maybe, even lack of intuition when it came to other races.) He is constantly trying to find someone to tell him what to do, and his actions are guided by that, he immediately leaps to serve the one with most authority. This is extremely evident when the Animorphs put him in a position of leadership and try to get him to tell him what to do, and its one of the few times he ever lashes out in anger in the series because he can't handle being in that spotlight. While I think his decision to serve solely Jake was the right decision, I think he made it out of extreme insecurity in his own decisions (thought it was definitely reinforced by the betrayal.)
[spoiler] This is a theme that reoccurs throughout the entire series, in MM3 when he notices something is wrong with the battle that got Jake killed, he refused to act on his actions even though he suspected something was wrong and left him partially responsible for Jake's death. And he repeats the pattern in his final book when he struggles between taking another leader and continuing to follow Jake. Even in the last book, he doesn't seem completely comfortable in his new leadership position. [/spoiler]
7. As I stated above, I think Ax is a soldier first and independent second. Whenever he breaks out of that role, he usually immediately snaps back to a soldier position with massive apologies and shame (which is rather uncharacteristic of Andalites), which I think is where the relationship is stabilized between Ax and Jake. Jake knows that when Ax screws up he is always going to snap back in line, just like the rest of the Animorphs for the most part. I don't think Jake and Ax ever really surpass a 'business' relationship level of friendship, which further stabilizes the relationship between them. All of the Animorphs have their problems within the group, and I think this is where Jake proves he is a real leader, because he knows what they are, and for the most part how to deal with them.
8. Personally, I wouldn't have after they forced me to take the blame after they wanted me to take the blame for something I didn't do. Also, I like to think I would be a little more appreciative of the Animorphs helping me live on a planet completely foreign to me and I would want to make sure their wishes were considered before I took any course of action. Of course, not being Andalite, I don't know how deeply blind allegiance is ingrained into the head of their youth. And there's no knowing what someone would do after being cut off from your own people that long, its possible that pure loneliness could have dictated Ax's actions, which is understandable. As for what I would do the mend the relationship after the faux pas, I think I would have done what Ax did. Said I was really sorry and promise never to do it again, though I think I'd try to take a little bit more active of a role in helping earth instead of just being a yes man.
9. Probably a couple months ago. Honestly, the only thing I'm really concerned about them changing is the stupid Kafit bird thing. Either take out Ax's paranoia, or explain it away as him being stupidly paranoid. (Or, could make it a psychic anomaly or something, lol.) What I would like to see in a re-release is at least some discovery of the motive behind the captains actions, and the explanation of how exactly the Yeerks are tied to the Andalite homeworld and the Andalite rebels themselves.