I think you're way overstating the case with Eddie, he's not "abusive". He obviously has a temper and the show wants to show us that, and how it probably had an effect on his son, but jeez, calm down, not every imperfect social interaction or instance of minor emotional neglect amounts to abuse.
I actually think constantly talking about Mandy being a victim of abuse and that she needs to leave Eddie is taking agency away from her, like she's also a person who makes choices. And your disgust of Eddie is actually making you miss what's really going on, what Eddie and Mandy are actually feeling.
It was kind of hard for me to get through this reaction with you because I think you're way too judgmental and have way too high expectations of parents, to the point that I think you partly misunderstood the point of the show, and this episode in particular.
The thing that probably rubs you the wrong way, and I get that, is that Eddie's clearly "the man of the house" or whatever, like yes, he's pretty macho and maybe more often than not has the say in the family. But it's not like his wife seems to mind that, I think she's mostly fine with that and I think it's just their dynamic, and you need to accept and respect that as well, even if it's not your idea of a well-balanced relationship or what you would look for in a guy. We can see that they obviously genuinely love each other and Mandy doesn't come across like an abuse victim at all to me or like she's scared of him or something, like it would be the case if he was actually abusive.
And obviously this is all a very emotional time for the family, it's clear to me that Eddie's not usually this high-strung, like I don't know how you got the impression that this is how things usually are between them. Unfortunately, in our society men are often made to feel like the only emotion that is socially acceptable for them to display is anger, and I think it's pretty obvious that that's what we're seeing here, he's channeling his grief into anger and rage. And only when he's alone in Jamie's room does he also let himself feel the sadness. Which is not a good thing and it's unfair to Mandy and Lisa but it's also understandable on an emotional level.
All in all, I think it's pretty clear that the show wants us to feel that it really wasn't the parents' fault; yes, they made Jamie, and yes, parents are always influencing their kids, and yes, Eddie's temper and prototypical male macho behaviour obviously had an effect on Jamie. But Eddie's not really better or worse than all the other dads whose sons don't turn out to be murderers. And like Mandy said, they also made Lisa, who is sweet and kind and emotionally intelligent. I guess according to you, they are responsible for Jamie being a misogynist murderer but not for Lisa being an overall well-adjusted person?
It's not helpful or fair criticizing parents for every minor mistake they make, like parents are also just human, which is mostly the point of the show. To leave this episode with the sense that "oh yeah, it was obviously and completely Eddie's fault that Jamie turned out this way, and yeah he should feel bad" is frankly astonishing, I don't know how anyone could come to that conclusion, and I think it's a complete misread of the text.