I think your email to your father is a brilliant piece of logic, using the WT's own words--and not taken out of context either! (I hate when the WT claims that apostates twist words and take them out of context when the WT is the biggest culprit in the known universe for doing that.)
This business of God reading hearts and not merely saving JWs is how reasonable JWs try to get around the undeniable official teaching of the WT that only those marked on the forehead as per Ezekiel will be saved. The mark is baptism as a JW and not just that, but living up to your baptism. Many years ago, when I was still pioneering and uber-zealous, our CO said something from the platform that made me shudder. He had us read the prophecy in Ezekiel about the man with the secretary's inkhorn who went around marking those who where sighing and crying over the detestable things being done. What happened after that? The angels with "smashing instruments," ie big hammers, went around smashing in skulls of anyone w/o the mark. You see, the mark is on the forehead so it's really easy to see and the angels won't be mistaken.
Then he said that if we ever felt we were losing our sense of urgency, we should go stand outside an elementary school playground for a while and just watch all the happy little children playing. THen we were to imagine the angels coming down with big hammers and smashing all their little heads in.
I'm not kidding. That was part of his talk from the platform (probably mid 1990's). I remember feeling slightly ill at the time, thinking (but suppressing) that something had to be wrong...