Thanks Paul for sharing this incredibly moving experience. Since you're from a multi-generational JW family, that must mean your dad, in addition to enduring the pain of loss of you and your family, also has to grapple with the guilt of feeling he has betrayed all of the family values inculcated in him.
Please take solace in the fact that he is at least awakened and mentally free (late perhaps, but never too late); encourage him not to recriminate himself but just move toward the periphery, a bit closer to the door.