" I need to stop obsessing "
This is a very big investment for you, and I'm not just talking money. So while she's under development, this is the time to be absolutely sure everything is right. So it's perfectly natural and ok to obsess.
" I wish I could nail down exactly what isn't right. They nailed the digital sculpt but something is slightly off in silicone. It's close but not quite there. I don't have an artists eye to be able to identify it. "
Personally, I think its pretty much all makeup, hair and lighting at this point. Also consider that we're comparing an almost un made up face, to one that is fully made up. Have a peek at before and after pics of women with and without their makeup and you'll see what I mean.
Here are a few subtleties with how the sclupt is originally displayed, that could be at play here:
Hair:
One thing that stands out is the sculpts head appears rounder, but this is strictly because of the bangs on the wig she's shown in, and not an issue with the sculpt.
Also the wig hides most of her eyebrows, which is also a big factor.
Once you put a wig on her that's closer to the model's, it will lengthen her head and reveal those eyebrows, making her look that much closer to the model!
I think this is going to make a HUGE difference here, because this will completely change the outline and shape of the sculpts head, making it like the model's
" I played around with faceapp for a while. It seems I can't thicken the upper lip much if at all. "
Makeup:
Personally, I think the thickness of the lips is right. What appears to be the biggest difference to me is the contour of her upper lip line. Looking close at the model's pics, I think the sculpt is right on to the model's natural lip line. The difference I see is in how the model is made up. Specifically the line from the center "divit" to the corner. It appears to be a straighter line on the model's lip liner than the sculpt.
At this point, I think this is very subtle now when looking at your last pics.
" My very first impression was that the nose is huge. "
Lighting and makeup may have an effect here as well:
The width of the bridge and the tip of the nose of the sculpt might be a little wider than the model. If so, I think a little subtle shading with makeup will bring that closer to how the model's nose is made up.
To see what I'm thinking, have a peek at makeup videos where women use subtle shading to narrow their noses. And it may very well be that the model's makeup might also be done this way.
Again, at this point, I think this is pretty subtle when looking at your last pics.
Something else to consider,
As we have seen many times, no two doll heads of the same model number, turn out perfectly alike. Even if photos are sent in to have one copied. There's always some subtle differences in the makeup. The only way I've ever seen two doll heads of the same model number turn out as 100% perfect twins is if they are made, and made up at the same time by the same artist.
Also, do you have shots of the model from other photosets, especially where her makeup and hair are different. If so, compare those to the examples you show here. It's possible you might even see some noticeable differences there.
All in all, This is very cool and exciting! I will say this again because I think you are on the right track. Every step you made with your virtual makeup attempts brought your doll's head much closer and closer to the real model. Your just fine tuning the the sculpt the way a makeup artist fine tunes a model's morning face to her made up face.
Congratulations my friend! You have a very sexy babe on her way to you soon!
Cheers my good buddy!
