Heh, I think the "Friedrich was forced to learn Latin" bit amused me the most. If only!

As for the letter to Wilhelmine, [personal profile] cahn, I think you're thinking of the one he wrote to her after the engagement ceremony, not the marriage,

But he did write one in the marriage night, too, at midnight - the "thank God that's over with, you are the first one I write to, I still only love you" one. No mention of a nightly walk, though.