Obviously a child's future cannot be solely based on his/her attachment to the mother. An interesting article I read mentioned that physical abuse especially to the forehead can cause damage to the prefontal cortex which is responsible for moral judgements and personality. So hitting the child's head can cause damage to this area and lead to a lot of problems. There was even a case where a murderer escaped the death penalty because brain scans showed that his prefrontal cortex was damaged.
I love that you related this development lab back to brain function, because that is the kind of stuff I like the most about psychology. And yes exactly, the prefrontal cortex is responsible for most of our higher-order cognitive processes, the stuff that really makes us human. And this reminds me of the story of Phineas Gage, which I believe we did talk about in this class. Damage to his frontal lobe led to drastic personality changes, so I can see how your explanation about abuse to the forehead is totally possible.
While I do agree with you that it could be a case where damage to the head could make a child not feel attached, you forget that after the damage, the child might still be conscious of what is around him. Therefore, the child could still be nurtred even if he doesn't even know it. Besides, the damage to head would probably would make the child even more attached as they would be feeling a stronger sense of security.
It makes sense for prefrontal cortex damage to lead to psychological problems, and I feel it does affect well-being. How, though, is slightly more complicated. On one hand, a drop in judgement could lead to a multitude of mistakes in life, leading to a worse-off well-being. The alternative, is that the shift in personality changes how a person views life, so that what would be a low well-being improves with a different outlook based on personality.