Absolutely agree but my figures, were approximations over breakfast coffee. It is indeed possible that the IAS and therefore ROD could have been higher, and that in turn would have required yet more height, height they did not have, to ensure a successful ejection.
I still think it incredible that the pilot survived without, it appears, a full chute.
That said, this accident video certainly reinforces the message in the USAF training film I referred to earlier, that in certain ejection circumstances seconds, fractions of seconds , of delay can mean the difference between life and death.