Monitoring only works if the person being monitored is in stable, long-term employment - that is the only way to detect behaviour patterns that are not normal for that individual.
Secondly, if a person reaches their limit, and yet is lucid enough to get in an aircraft and fly it perfectly competently to the scene of the crime, they have clearly made a series of quite deliberate bad decisions. You can't entirely excuse those decisions on the basis of his personal life, or perceived status as aviation hero and all-round great chap.
I think you only really find out a persons true character when they are under tremendous stress. This is certainly true in aviation - some fight all the way to the end, others give up when it all gets too hard. I remember watching the program about the Alaska Airlines MD80 that lost elevator control - those guys were still thinking and fighting all the way to the end. They never gave up.
In the current case, this guy lost it in the face of severe personal stress and chose the wrong path entirely. Some of you here may like him or count him as your friend, but I am afraid he has displayed the opposite qualities to those you would expect.
I feel desperately sorry for him, and wish I could help in some way - but I would never, ever want this guy flying my family around. Sorry.