My translation (ESV) says "through" also, but even in Young's translation, it says that baptism (the antitype) "doth now save you."  The point is that baptism saves, whether that may happen "by" or "through" the actual water.  This quote from Luther's Small Catechism may help to explain where I'm coming from:

Martin Luther wrote: How can water do such great things? Certainly not just water, but the Word of God in and with the water does these things, along with the faith which trusts the Word of God in the water.  For without God's Word, the water is plain water and no baptism, but with the Word of God it is a baptism, that is, a life-giving water, rich in grace, and a washing of rebirth in the Holy Spirit, as St. Paul writes in Romans chapter 6...

And thus follows the passage which I mistakenly quoted as Titus 3:5-8. 

As far as your other responses go, well, I don't have much to say in return at the moment, as I haven't really studied these things as much as you have.

I think I already did above but I'll go for it again.  In a universe without God or the supernatural, when a person dies, their consciousness is wiped out.  None of what they did in life has any significance any more, because it has ended in death.  When someone has a dream, no matter how remarkable the dream is, it has no effect on the person if their memory of the dream is gone.  If death is the end, life is merely a forgotten dream.  The end of something, it's final goal and outcome, it what determines its significance.  Even if we accept the saying that "the journey is what matters, not the destination," we can still say that the significance is in the final outcome, because the final outcome of the journey is not the destination, but the experiences and lessons learned from the journey.  The final outcome of life is death.  Since life cannot be remembered after death, the experiences and lessons of life no longer have any significance.  Neither do they have significance to the lives of others, because they will all die also.

Sorry for the late (really late) reply to this, Rob, I got kind of busy in the days following this discussion.

The literal translation says that baptism is "a question of a good conscience in regard to God," leaving it ambiguous whether it is a demonstration of a good conscience, or a request for one.  The ESV translates it as "an appeal to God for a clear conscience," not that the statement must be understood that way, but it shows that the clause could be interpreted differently.  Before that, when Peter says that baptism is "not a putting away of the filth of flesh," he doesn't imply that baptism doesn't cleanse spiritually, but that it's not a mere physical cleansing.  Baptism is indeed an act of obedience, but so is faith, and I think we would both agree that we are saved through faith.  On the human level, both faith and baptism appear to be human acts and choices, but faith is a gift of God, and humans cannot choose God for themselves.  Likewise, the true work of baptism is not accomplished by man, but by God, who saves by water and the word.

That brings me to your next point, that the passage could be taken as synecdoche.  First of all, I don't mean to say that a mere dunking in water can save someone.  Baptism is more than plain water; as I pointed out with my Luther quote above, "it is the water included in God's command and combined with God's word.  Without the word of God, the water is plain water and no baptism."  God has many ways of imparting grace to his children; he gives grace through his Word, confession and absolution, the Lord's Supper, and Baptism.  Yes, they're all elements of the same Christian narrative, but they also are all means of grace, which give grace to us in different ways. 

Yes, they would affect the lives of others, but still would lack significance because the lives of others would be meaningless as well.

I wonder...