Thanks, Death, and I have to say that of the criticisms I've read so far, yours are the most substantive. They go past Winegardner being a sonufabitch or something and speak to real issues. So I'll answer on that level:
1.) I can agree that Geraci's relationship with his grumpy-ass father was quite memorable, but there were other memorable characters as well. Mickey "Cahn-sig-liary" Shea was one; Joe Lucadello was another. Not everyone was, though. Russo could have been more interesting as a character, though the whole "Fuckface" bit did make him a little memorable. Forlenza was a total no-interest character, though, to be fair to you.
2.) The "wood" line. I'm married, and we say stupid things like that constantly. But to speak to the central point you made, you've as much as said that what bothers you about the state of their marriage in late 1955 is that it wasn't fitting in with HOW YOU SAW IT. Yes, a case could be made that, four months after realizing that Michael lied to her face and fleeing to New Hampshire until Hagen got her to come back, Kay'd be a little more cold to him still. But that's asking human relationships to be consistent and have a proper through-line, and they don't. I've only been married for eight months, and I sometimes already want out. Then the next weekend we're happy as all get-out again. But as a side note, it wasn't entirely Winegardner's own creation; Puzo has her taking up Catholicism and becoming the Corleone equivalent of a stepford wife. The precedent is there.
3.) OK, the gay thing. I have to admit that it took me some time to get used to the idea too. And there may be something else at work here: Winegardner's need to comment on things relevant to our time by using their equivalents in other times (no matter who the author is, every story about a certain time period is really about the concerns of the people expected to read it), in this case the issue of pedophilic priests in the Catholic Church. Remember that the first mention of anything hinky is when Fredo, at ten, wants to become a priest by studying under Father Stefano, and then he suddenly emerges at thirteen strong, serious, powerful, and shy around women. One day he's just clumsy, then one day he goes off into his room for long periods of time. Finally, at sixteen, he announces that he no longer wants to be a priest and ends up joining the family business. One admittedly has to read between the lines, but it can be argued that Winegardner at least laid the groundwork. As to how it changes the character of Fredo and offers an explanation for his weakness he didn't need, I can't comment either for or against that. It's a valid opinion.
4.) The abortion/miscarriage thing, I totally agree with you; it should have remained an abortion. But the argument I could offer is that Kay was still standing up to Michael, whether the abortion was real or not. She wants out of this marriage, period. She knows she cannot stay with this man. She knows that if Michael thinks he has to, he will make her a prisoner again. He will never change. And he will never allow her to leave, unless she tells him what she has decided to tell him, even if it is a lie. And it works; the marriage is already on the rocks, and now it's ended. They divorce. It brings nothing to the story, really, but it does briong something to the color of the piece, and that may not matter, but it's all I have on that one.
5.) With Clemenza dying, that may not have been as planted as you think. The script for Godfather Part II said outright that Clemenza's heart attack was real, that it came from stress related to the troubles the Rosatos were giving to him. Pentangeli said to Michael: "Sure, Pete Clemenza died of a heart attack, but the Rosato Brothers gave it to him." He later said to one of the Rosatos: "You drove old Pete Clemenza to his grave, Carmine; you and your brother. Turning on him; trouble in his territories, you and your demands. I hold you responsible, just as though you shot him in the head. And I ain’t gonna let that go for long!" That's all in the script, if not the finished film, so it can be argued that the intent, at least, from the beginning was that Clemenza really did die of a heart attack, no matter what Cicci said (he really died from his actor being unreasonable, but what're ya gonna do?).
6.) Finally, regarding Hagen: I have seen nothing in Part III to indicate that he died of a heart attack, or any other cause of death. The only mention of Hagen dying in the film is Michael telling B.J. Harrison that he didn't live to see the ordination of his son Andrew Hagen (well played by John Savage in a brief role; he gets the Robert Duvall voice down perfectly). But that's all; the rest is an open slate. And determining that he might as well cover Hagen's established death, Winegardner chose to do so in the most heart-wrenching manner he could, and to me, it was just that. I'm sorry you felt it was lame, but I'm not sure how a simple heart attack is an improvement.
Finally, not to sound like I'm lecturing, or talking down to you, but if you only read 150 pages into the book, and then gave up, can you really have the most imformed opinion you can get? Just give it another shot; you don't have to change your opinions at all if you don't want to, but at least you'll know they're fully-informed opinions. We can still disagree, but you'll have more ammo. And there's no harm in that.
