JMB is no saint. He will tell you that himself. However, I don't think that he had anything to do with Melissa's death. She may have died of the stress from the murders. IOW, she may have died of a broken heart. I recently remember hearing a story on TV about how that is possible after an extremely stressful event. I think the murder of your child would fit the bill as an extremely stressful event.
Have you seen/heard JMB speak recently? He looks and sounds different. It's nobody's business what happened, but I believe that his brain tumor, if not removed surgically, is being treated by medicine. Magic? I don't know if I'd go that far. Probably just different.
I used to believe that JMB killed the boys, but believing that, I now realize, is just as wrong as believing that Damien, Jason and Jessie killed them. Why? Because, just like with D, J & J, there is no evidence that implicates JMB, just innuendo - and his own misbehavior. IMO, since the mtDNA of someone close to one of the boys was found at the discovery ditch, the identity of the killer is pretty obvious.