Rob, I think she's is beautiful like that... But I do understand you want to be as close as possible. We can't deny the speckles looks much finer on the original with those comparison pics and that it looks darker.
After all that's a hobby and not a race, you have all the time and if you wish to get it as accurate as possible, so star again !
I know that's the kind of thing which can obsess you after the model is finished and you'll regret to not have redone it.
But in some case, the second (or in your case the Xth attempt

) is not better than the previous one and sometimes even worse... So please try on scrap before starting over on the DS. I ruined my Red 3 like that, thinking I could do a hell of Blue Leader from it, and now I regret because I failed
Have you tried to mix different way to have the speckle done ?
I mean do some passes with an airbrush to get fine speckles and rattle cans for the biggest ? And this way you could have a larger range of grays that would suit your DS.
That's just an idea, but before doing the speckles job, I would put a slightly darker layer than the basecoat to be sure it will be darker.
I wish I was in CA to give you a hand...
Please don't give up ! :thumbsup