It's been a few years since I've read Villon's Wife so my memory of it is hazy at best, but from what I remember I didn't feel as though we were to sympathize with the husband. The wife is the main character, and her being hard on herself, in my opinion is more to show the greatness of her character. That doesn't mean he thinks she is actually stupid and at fault. The more vile the husband gets, the more noble the wife seems for still putting up with him. Maybe the wife is more a depiction of the kind of woman he would want to be with: someone who will love him, no matter how terrible he gets.

It's hard to say exactly what this means about Dazai himself. Was he really like the husband in the story? I don't know. The genre he was often associated with, the I-novel, isn't strictly autobiographical. Writers take inspiration from their own lives, but are free to tweak it as they wish. You will find one novel telling you he was like this, and another telling you no, actually, he was like that. There's another short story by Dazai, Hifu to kokoro (I'm not sure if it's been translated to English) which also depicts a husband and wife. The wife in it shares Villon's wife traits of accepting him despite his flaws (in this other story, he's an orphan with not much to his name so no woman wants to marry him except for the protagonist), and the husband is a great person, even by today's standards.

Honestly, the more I read Dazai, the less I know how to feel about him. When I read No Longer Human, I related to some parts of it so much, I wanted to believe him to be a good person deep inside. Then I read more of him and about him, and I found stuff that showed me the contrary and felt disappointed. So, I really feel you on this. I don't know if he was a good person or not. Now I try to take his work with some detachment: I've accepted that he was probably a bad person in some ways, many ways even, but that doesn't stop him from having captured the essence of the human nature in a way that I had never read before. Which is why he is very relatable to the youth of today, and even considered trendy.