look at it from her point of view: her husband became ****ing crazy, yelling, irresponsible and unpredictable. 

But who drove him to this? Prior to him lashing out and becoming unpredictable, he was because a doormat for her to walk all over him and he took it, never once putting his foot down and standing up for himself. And as I remember it, wasn't it for 20 years or so? That's a long time to basically be one's b*tch. He only "came alive" once he became smitten with Mena's character. She woke something him inside of him that has been lost for years. Finally, he wanted to start living again and since she wasn't going to change her ways, he set out to do things he has always wanted to do, whatever that was. He actually tried to get Annette's character to embraced this newly awakened Lester and for a split second, it looked like she would. That is until the couch issue brought everything to a crashing halt. It's this very moment when he realized that she wouldn't changed. Now threatening her with financial instability, she doesn't have a leg to stand on given her infidelity.

Let's agree that it could go either way. I think both points are valid. The big question though is this: Did you get the significance of what Wes' character was looking at when he looks closely at Lester? A lot of people never pick up on it's meaning, even friends of mine that have seen it totally missed the point.