By using a light meter as if it were a densitometer, you seem to have arrived at a density of 0.1 for the low frame and a density of 1.3 for the highlight. Flare could be messing with the result accuracy, but seems ballpark ok to me.

Followed a graph of my own (of a 400 speed film) with my fingertip up 7 stops from 0.1 ... I also came up with a density around 1.3. My graph measured 0.55 CI, and is a little "under" box speed development.

Suppose you lost speed like I did when I developed to 0.55 CI, then the speed might be approximately EI 250

Nice, you appear to have been lucky...