Should I purchase the JR Pass

Hi there, would appreciate help on this! The following is my itinerary and I need help in deciding whether to get the JR Pass, and when to activate it!

I'll be travelling from 22 Dec to 5 Jan
22 Dec - 28 Dec Hokkaido
28 Dec - 2 Jan Tokyo
2 Jan - 3 Jan Osaka

22 Dec - Touchdown Sapporo CTS Airport, taking Resort Liner Direct Bus arranged by Hotel to Niseko resort for skiing

23 - 25 Dec - Around Niseko Resort to ski

26 Dec - Day trip (haven't decide)

27 Dec - Check out from Niseko to travel to Sapporo Mitsui Hotel
Google maps stated this route:
Hirafu Welcome Center to JR Kutchan Eki via Kutchan Line
Kutchan Station to Otaru Station via Hakodate Line
Otaru Station to Sapporo Station via Rapid Airport Line
(How much would this journey cost approximately?)

28 Dec - Check out from Sapporo Mitsui Hotel to CTS Airport:
Sapporo Station to New Chitose Airport via Rapid Airport Line

Upon arrival at Tokyo Narita Airport:
Narita airport to Nishi-Oi Station for airbnb via these 2 routes
(1) Narita to Tokyo station via Narita Express Line + Tokyo station to Nishi-Oi station via Yokosuka Line (2) Narita to Nishi-Oi Station via Narita Line, Sobu Line, Yokosuka Line (longer route but do not need to change)

28 Dec to 2 Jan Tour around Tokyo
- Taking Joetsu Shinkansen and get off at Gala Yuzawa Station for skiing

2 Jan - Take Shinkansen Bullet Train to Osaka

3 Jan - Tour around Osaka

4 Jan Rent a car to Nara & Kyoto and back to Osaka airport till 5 Jan

Thank you for your advice!!