The last quarter of The Lost Time should have been cut from the song. It would have made the song much more listenable without the repetitiveness at the end, because the verses are absolutely beautiful.
Sales of Sweeter Than Fiction could be used as a test to see if the Lord has lost fans because of the negative publicity this era
If the song is good I think the fans will be there for it. New fans could be gained if it shows her in a different light from stuff she has done previously.
I don't think how this sells is any indication of her future singles success at all. I mean, does anyone really think because of "Oh La La" that Britney is going to flop with her next single? Soundtrack singles/collaborations never really go in line with the rest of an artists discography.