Glad you think that your list of "things I might never know" has been reduced by one.
Can I add a new thing to your list? The letter you have you said was dated 8 July 1944, but Rennes wasn't liberated until 4 August 1944 - do you think that she just got the date wrong, or started the letter before liberation and finished after?
PS. There is various footage of Jean Marin giving a speech to the newly liberated town from the balcony in Rennes town square and he is named in the Army Pictorial Service description of footage they took.