I feel like I read about a scenario like this in a book of urban legends. The situation given was a worker in a plant who got dragged halfway into some machinery and horribly mangled before they managed to turn it off. Certain to die, couldn’t extricate him, etc.
The solution presented was to call in his wife for a last goodbye and then turn the machine back on.
I’d vote not guilty, at least of 2nd degree murder. Jack could be a sociopathic, lying sack of crap who tortured and murdered her in cold blood, but there’s no more evidence of that than of his justification of his motive.