I agree to an extent with everything you say, except that this isn't "normal".
At the end of the day, it's a working class family doing their best. The only roadmap they have is the traditional one laid out before them. Dad is attempting to break the cycle of abuse and has been successful in not passing down physical abuse, but hasn't perfectly managed to control his anger. His Mum is copying the same pattern she probably grew up with, where her role is to take care of everyone's emotions and Jamie appears to be fine.
There are millions of similar families, and in 90% of them, the kids will grow up, recognise that their parents tried but didn't always get it right, and try to improve on that again for the next generation.
I think the problem is that the online space- which many parents don't understand or perceive as dangerous- is full of rhetoric aimed at capturing young people whilst they are still vulnerable and full of hormones and anger and confusion, and radicalising them before they get to adulthood.
If there wasn't millions of potential Jamies living in millions of similar homes, then Adolescence wouldn't have been relevant.