You weren't the only one to shed a tear. And personally, I thought the ending was great. To give a fleshed-out conclusion to each character wouldn't make sense and would've made the film well over 2 hours. It wouldn't be right because, as much as you as an audience member would like, there isn't always a clear-cut conclusion. The Truby's son still has sexual issues and will probably have them for a long time. Hannah Clint will always be a self-absorbed, slutty popular girl. Don and Helen's story was wrapped up in a truly genius way. Like Don says, they could have the generic married couple fight about love and life and the meaning of it all, or they could shut the f--k up and eat their eggs.
On the other hand, some characters did get the ending you wanted each one to get. For example, Allison (the malnourished girl) threw a rock through the jerk's window. While that may seem inconsequential, it's powerful precisely because of that: this is a girl who's let jerky guys walk all over her and only finds her self-worth in boys who don't respect her. By throwing the rock through the window, instead of going in and having sex with him again, she's finally standing up for herself.
Even more so, the Mooneys and Jennifer Garner/her daughter got even more thought-out conclusions. We see that Tim survived, his father understands that football isn't an option anymore, and the girl still loves him. While his future is uncertain, there is hope. As for Kent, he's stopped judging Judy Greer and is giving her - and love - another chance.
And Jennifer Garner finally realized what a monster she had been and the very last shot of the film nicely wraps up her story.
I agree, the movie ended better than the book, in which we just started watching these people, and then ten weeks later stopped.
Halfway through the movie I'm thinking, "Who should I be rooting for? Who's the protagonist? Who's the antagonist?" In the second half Tim and Brandy started to provide that, and I did shed a tear at how badly her mother treated Tim and how it almost killed him. The movie did give their story line better closure, in the ways you mentioned, and I think especially by letting Mrs. Beltmyer see how her actions had serious consequences.
I think especially by letting Mrs. Beltmyer see how her actions had serious consequences
I like how while she's realizing that, the narrator is talking about the blue dot Carl Sagan thing, which Tim used to say how nothing matters.