Yes, and he will likely keep it until after USO.
Almost certainly. 1000 of Djokovic's current points come from Canada, 600 from Cincy, and 2000 from the USO. So even if he defends all of that, the most he could gain
would be a mere 400 points (not enough realistically to reclaim #1).
Federer, on the other hand, has just 90 from Canada, 180 from Cincy, and 720 from the USO. That's 990 to Djokovic's 3600 -- with huge room for improvement...