no, it is not too far for Summer
stay near Asahikawa JR, which is southern part of city, easier to get out (regardless Asahikawa city traffic is much lesser than Sapporo)
within 1 hr, u shld reach Biei, then work your way down to Furano (or vice versa)
bcos the whole stretch, will be dotted with "sights" ... some not so easy to find ... so it wont appear to be long drive
start off early
i recall Blue Pond lighting is best late afternoon, when the sun is behind u .. in the morning, u r looking into the sun
wow $488 is really ex ... Summer is peak season there, due to flowers .. even Dormy Inn Furano is $300+