Hello David,
It is interesting that you say you're a physical scientist. I am too. I wonder sometimes if I wasn't attracted to science because the facts and theories are so objective and analytical to me; I can lose myself in it because they cannot be disputed, and just "feel right" to me.
Anyway, about your letter to N. Dad. I wrote one too. It was 35 pages and counting...I read it the next day and realized all of it would fall on deaf ears, but it was very comforting to me to write it. I started by-- first thing in the morning as I woke up, I wrote down the first thought I had and the subsequent feeling. I realized I had some memory or thought about my parents the minute I woke up and often throughout the day the would creep in at the strangest moments, and the corresponding feeling was always fear, anxiety, or the like.. I did this for one whole day. I recorded every thought I could and every subsequent feeling. It was strange, but looking back at my list I could see that I was preoccupied with thoughts about the Ns in my life, and all of the feelings associated with thinking about them weren't pleasant or desirable. But there were also lots of good thoughts and feelings which mostly centered around my SO and my dog (loves me unconditionally). I allowed myself to not feel guilty for having all the negative or unpleasant thoughts and feelings..I just recorded them, and as I had each one I tried to realize that I was in fact thinking it, and that it was OK (all feelings are OK), and then let it go. I then composed this list into a letter to send to Mom and Dad. This was going to "prove" to them that I didn't think at all like they thought I should (I should be more giving to them and less selfish--be Less Less Less!), and my behaviors didn't even mean what they kept insisting they did (ie, you didn't offer to help out with your sister's shower, which means you don't care about her, etc), and it was intended to reveal to them, my true feelings...
How did you compose yours?