The only way it will be less than 40 weeks is if it gets certified on the basis that it has enough shipments to make up for the rest of the sales. The tour isn't having a noticeable effect on the sales or chart position right now, so I doubt it will for the rest of its run
The album is receiving an effect from the tour. Why do you think it's Top 90 on iTunes? I really doubt it's because of the single.
I think NL had decent life. Top 40 is not bad for Demi's first 3rd single. At least it exceeded the expectations...
Now I want a ballad for final single. DEMI is full of ballads- it's time for one of them!
Nightingale?