So after a bit more reading this is the itinerary I have so far:
Tuesday 14th August:
Land and go to Sapporo. I plan to book an Airbnb apartment not far from Susukino for restaurant and night life.
Wednesday 15th August
Book tour to Furano. I will be a bit jet lagged so a tour might be easier especially as I will be using public transports. This one looks ok.https://m.viator.com/tours/Sapporo/A-Must-visit-spots-in-Hokkaido-Fura...
Thursday 16th August
Go to Josankei from Sapporo. Possible tour:https://m.viator.com/tours/Sapporo/Mountain-Bike-Tour-from-Sapporo-Inc...
Friday 17th August
Half a day in Otaru. Seafood at the market and maybe a rickshaw tour. Then back to Sapporo.
Saturday 18th August
Morning: Travel to Noboribetsu. Stay at Dai-Ichi Takimotokan.
Afternoon: walk through Hell Valley and Noboribetsu onsen town. Onsen and dinner at the hotel.
Sunday 19th August
Morning: Travel to Lake Toya. This seem to be a bit painful. Bus to JR station. JR to Toya Station. Then bus to Toya Lake.
Ideally I would like to stay at Pension Ohno but it seem a bit far from the bus terminal (35 min)as it is on the way to the ropeway. Taxi could be possible.
Monday 20th August
From Pension Ohno. Go to Toya Lake center. Take ferry to island and discover island.
Then Onsen at Toya Kanko Hotel. Then back to Pension Ohno. I have seen people saying that they had to walk on the road to get there from town but I am assuming that there must be a path next to the lake we can take if we donüft have luggage.
Tuesday 21th August
Back to JR station for JR to Hakodate. Stay in hotel near the market. Spend the afternoon at Goryokaku. Then at night ropeway and views of Hadokate.
Wednesday 22nd August
Day in Hakodate. Morning market for seafood.
Discover the city. Possibly a last onsen. Any recommendations?
Thursday 23rd August
Any thoughts on this itinerary? I am now keen on everything on there but I am afraid I am trying to do too much and it will be too tiring. The other option would be not to go to Hakodate and to extend my stay in Sapporo and Noboribetsu one more day each.
I used HyperDia to calculate the cost of all the travelling bubble JR but unless I got it wrong it seems cheaper not to get the card, which I find surprising. In that case should I buy all the tickets when arriving at the airport on the first day?
Thanks for all your help.