JR East South Hokkaido Pass

Hi, we are visiting Japan this summer. Our itinerary will be Tokyo-Hakodate-Sapporo, Otaru, Biei, Furano, and back to Tokyo
Please advise if buying JR East South Hakodate Pass is the right way to do and save.
Aside from the Shinkansen from Tokyo up to Hakodate, will I be able to use this specific JR pass going up to Sapporo and the other places mentioned above?
I don't see this JR pass being offered for sale in your site. Is there a specific website that offers this pass?

Thank you