1) The Last is canon and you know it. It has been posted numerous times on this forum (even with a video I believe) that Kishimoto rewrote the story himself
2) About the timeline , we have debated this on some other thread also. Best case scenario , Naruto became Hokage between the ending scene of the Last (where Himawari and Bolt are running towards him) and 700. Now this has the following consequences :-
a)
Sakura could not be pregnant in this meeting as Bolt and Salad are roughly the same age. So the people who are saying that Sakura is the mother because ahe was pregnant are wrong.
b) If Salad was indeed Bolt's age at that time, she could roughly be in the 4-6 year range, in which case she should remember meeting Sasuke and being with him before that. She does not. Why ? Timeline error by Kishi or is it something else ? Now it could simply be error in timeline and she could really be Sasuke and Sakura's daughter. Or she may have something to her origin we dont know about and Kishimoto didn't actually screw up the timeline. This could also connect to the plot as to why Bald guy wanted her (maybe for some purpose related to her origin which we don't know about). Would also explain the loss of birth records. Or she could simply be Sasuke and Sakura's daughter and her birth may not be connected to plot. Either way , I will wait for clarification before jumping to conclusions