My suggestions here on your plan-
For a same day trip to Pangong, you will have to take a hired cab as finding shared taxi or bus will be very difficult. Leave early morning from Leh to enjoy the beauty on the way and to spend sometume at lake. Its around 150 km from Leh.
Doing Leh to Srinagar in one day and that too by unusual route via dah, batalik will be very difficult so better stay at kargil and move to Srinagar on the next day.
Overall your schedule is bit tight considering the days you have. I am afraid that you may face AMS on the trip specially on the visit to pangong. Wait for the comments from other devils.