Rest of the itinerary can be fitted around these dates - plan to spend 2 days sightseeing in Lhasa, see Shigatse and Gyantse, and trek between Ganden and Samye. Possibly add Lake Namtso or Yamdroktso.
Not going to EBC or Kailash, finish the trip in Lhasa.
I've been in contact with a few agents and have quotes. PM me or reply this thread if interested