ISB to Naran will take 5-6 hours on a continuous drive and if staying at road scenery which u must stay and enjoy, then it will take almost 8-9 hours of drive and yes Day 1 is correctly calculated. Night stay should be in Naran because It's very romantic moment of the tour that you have to sleep with your blanket on you.
For Day 2, if you don't want to explore Naran, calculations are perfect. Start an early morning journey and on a continuous drive you will be in Hunza after a travel of about 8-9 hours, but with scenic values , add 2-3 more hours to it. Stay in Hunza.
Day 3 is your visiting day, spend as much time as you want.
Day 4 is also a busy driving day and you should go to Khunjrab Pass.
Day 5, yes for upper naltar valley, you have to hire a jeep.
Plan is good if you want to spend 5 days only on the Hunza Route.