I'm going to venture another answer and claim that the perfective-progressive discussion is a bit of a red herring.
Usually, since is a change-of-state verb, means "is dead" (perfective aspect) and not "is dying" (progressive aspect).
But in this case, I claim that is really a fixed construction and the difference between
> and
>
is one of emphasis, not one of perfective aspect. The first one could have been used here to mean a relatively neutral "I cannot die here". The second one adds emphasis and means something like:
> Damned if I'll die here
> I'm too busy to die yet
> I'd feel like a fool dying here
or some such.