I can reply only No:1 question.
From ISL to GILGIT 18-20 hrs.
Stay at Gilgit
Next Day start early & reach SOST Checkpost. It is 6 hrs from Gilgit i.e., 3 hrs to Hunza & 3 hrs more.
stay there & earl morning leave for China. Khunjerab Pass is 3 hrs drive from there.