You're more forgiving than I am, I'm still too horrified and very angry at this sorry excuse for a 'dad'.I am holding my judgement for now.
More likely, it was case of domestic violence and he killed his own children out of spite. In that case, he really is extremely dangerous and I hope he never ever gets parole.
But also possible that he really had a mental health break (as the mother said he was struggling with mental health) and harmed them in a psychotic episode or similar. In that case, the realization of what he has done might be worse punishment than anything the courts can do.
I understand what you're saying regarding a possible mental break.
But the fact that he did it three times -- makes me wonder ....
Imo.