I'm late to the party but let me congratulate you on finishing this work nevertheless. You deserve congratulations for your achievement: not merely the fact that you wrote a story, not merely the fact that you finished it, in spite of it taking almost three years (has it been that long already?), but the fact that you wrote a coherent story, tightly scripted, and wrote it exceedingly well. I have enjoyed the time I've spent reading it very much. As to your goal, to educate and entertain, I can certainly say that I have spent a lot of time trying to understand Sonny, what he did, why he did it and how he became the man he was. In that way, the story challenged me, which is a good thing.
I kept pace with your updates right up to the post describing Sonny's wedding. Read the first few lines that showed he was getting married, and then I had to leave for two weeks. Thus, when I came back (and finally came back to 'Into the West' specifically), I had the wedding scene, Tanney's attempted revenge and the final resolution all in one handy package. Quite a powerful ride to read those three pieces all together.
I have to admit that I read the wedding scene with a growing sense of nervousness. I knew the story demanded a repeat appearance by Tanney. In my mind, while the Pastor's words were soothing my conscious thought, my subconscious kept thinking of the wedding in Kill Bill. I assume you have seen it, or know of it: if so, you'll understand my worries. It made for a strange experience reading that post: on the one hand, all the happiness and seriousness that goes with any wedding, on the other the nervous dread that soon, everbody in the church would be dead.

Thankfully, it didn't happen.
I did notice Bert's comment about how Sonny and Will looked alike. As I read the next post, about Tanney's revenge attack, I was hit by a certain realization as soon as I read this:
His biggest worry was that he hardly recalled what the man looked like.
I instantly realized Will would die, so that Sonny would live and finally finish matters with Tanney. And so it happened.
Will's death, coming at so late a point in the story, was shocking. Also very shocking in the way it occured: no warning, no fairness, just sudden death. Although it makes great sense, both from a story perspective and from Tanney's point of view: Tanney would not have lived as long as he did, with all the enemies he made, if he'd been prone to bouts of 'honorable' shootouts at noon.
One final thought, something I take from the scene where Kitty and Sonny trap Tanney and kill him. This might be merely my personal view, it might not be at all what you intended. The execution is a pretty low-key affair. Yes, Sonny has his quote, yes, he goes into some exposition about Tanney killing Will, but all in all it's a quick, matter-of-fact deal. You did this, I'm going to stop you, BAM you're dead. Considering the epic of misery Sonny went through because of Tanney and Sonny's search for this man, all the suffering and death for all those years, this execution seems unequal to it, unable to balance the books. Which, in my mind, is just about right. Killing Tanney gives Sonny (and Kitty) some peace, but it doesn't give meaning to the misery that went before, or meaning to the life still to follow. It's not the killing, but the living afterwards - Sonny becoming a father - that finally restores balance to Sonny's life.
The rational part of me says that the final scene, showing Big Bend prosper and settle, showing Sonny as a father himself, is a very tidy and upbeat way to finish such a dark tale. The sentimental part of me says that it's only fair that Sonny finds happiness at last, after all that happened.
Once more, congratulations on writing this magnificent story. AARland will be different now that it's done.
