Code:
Day1: Delhi - Manali 500+ kms
Day2: Manali - Sarchu approx 200kms
Day3: Sarchu - Pang - Leh - again approx 240 kms
Do you really want to stretch yourself that much?
I suggest take it easy, why do you want to run away from the places in between manali and leh.
Rest all looks ok to me.