There are a lot of missing pieces at the moment.
If Lahabrea's primary concern was the wellbeing of his son, then his decision to kill Athena would have simply followed from that. And yet he decided to merge his soul with Athena in front of the boy, the main question on his mind being 'Did Athena truly love me?' So the murder of his wife wasn't really predicated on concern for his son's well-being, but rather the fact that she simply didn't love him. Otherwise the question itself would be irrelevant to the action that he took. Lahabrea spends a lot of time talking about Athena's 'influence' on Eric, without actually outlining how she did it.
Likewise, why seal away his own memories of the act? Emet and Igeyorhm had suspicions, but they would have no way of reading his memories since they were excised and safely stored in crystal. He deliberately withheld information from the rest of the Convocation and the people of Amaurot. And not only that, he tried to have Pandaemonium destroyed with his followers still inside only when there was a risk of the truth coming out. There's also the question of what he did with the red crystal with his sealed memories. Why not turn it in to the Convocation and be honest about the truth? It just seems a bit convenient to blame Athena as the source of all the evil in Lahabrea's pure, pure heart when the only thing that we can go off of is his word. Every story has another side to it, and we'll need to hear Athena's to judge for ourselves.
