Often when we get upset about issues as adults, we're being triggered by emotions we felt (but didn't know how to deal with) as children. For example, when I was a child I was molested by someone I loved and trusted. So, when my H (who had promised to love and cherish me) had a MLC and an OW, part of the misery and isolation I felt was actually caused by the abuse. Once I'd dealt with the abuse, and learned to distinguish what emotions were caused by the abuse and which by my H's betrayal, it was easier to feel empathy towards my H, and to stop feeling so isolated and GAL.
Similarly, my H had suppressed all his negative emotions towards his mother: guilt for "causing" his mother's rages, coupled with a desire to protect himself and fend her off. After he entered his MLC, if I got upset about something, he'd put up his hand as if to fend off blows from me: he'd started seeing me as the parental figure who he needed to fend off. At the same time, it was hard to separate the guilt for what he was doing to me from the guilt he felt towards his mother, because it caused such an overwhelming gut feeling of needing to escape. It was purely emotional, not logical.
It sounds to me as though your H's situation is quite similar. How did he speak about his mother when you first knew him? Was he able to express that anger, or did he act as though it had been no big deal, etc?
The pushing away does have to happen--they do need to get back to the place where they deal with their emotions on their own.
