Trip for Hokkaido

Hello,

Me and my partner are staying in Japan for a total of for 5 weeks from the end of july to the end of august. I stumbled upon an article saying they will be opening up Shinkansen to Hokkaido this march. As a train geek I thought why not visit Hokkaido. But damn, the distances between cities in Hokkaido are huge and they are way behind with their train network. Been very spoiled by Shinkansen from our last two trips last years.

This is how my itinerary looks like right now. (date/month)
Toko&Yokohama 27/7-4/8
Sendai 4/8-7/8 (activate JRP-7-days)
Hakodate 7/8-8/8
Sapporo 8/8-12/8
Okinawa 12/8-23/8
Tokyo 23/8-27/8
Home 27/8.

I can move a couple of days from Tokyo and Okinawa to max out Hokkaido. In Hakodate we're going to see Mt Hakodate and Lake Onuma. I suppose we can take an early train from Sendai to reach Hakodate before noon and do these two activities in one day.
Here comes the tricky part, how to plan the rest below in a smooth schedule from Hakodate? Rent a car or travel by train? Use Sapporo as a base? We are going with a 7 days JRP start with Senda. The old JR East-pass flexible 5 days would have fitted perfectly here. Shame it'll be discontinued this april. I also have a driving license so rent a car would be nice.

Need to plan in these below in my itinerary but don't know in what order and what's the best way to get there:
-Noboribetsu, visit the Bear Park
-Sapporo, minimum two nights to explore this nice city
-Otaru with coast Kanko Shakotan
-Farm Tomita and Blue Pond, near Furano

How about this plan?
-Train from Hakodate station to Noboribetsu. 3 hours. Lock in our luggage somewhere. Later on take train to Sapporo.
-Stay in Sapporo for 2-3 nights.
-Rent a car and drive to Otaru and the coast. Drive back to Sapporo same day but park the car by the hotel.
-Next day drive to Asahikawa or Furano, whichever has the nicest hotel. Visit Farm Tomita and Blue Pond.
-Next day drive to Sapporo Airport.
All in all 1night in Hakodate, 3 nights in Sapporo and one in Asahikawa or Furano.

Would love to visit Cape Sōya but don't think we will have the time. Is it worth the hassle to get up there and try to plan it?