60% is not consider as good, which should be in state nearto critical zone, your battery will be in shorter life, will not last longer,  change before you cannot start.
your service adviser is good as he/she inform the 60% level.

12.7v - 12.8v while engine not start is the best.

battery icon indicator on dashboard is not accurate.

Not at all bro? Like going over small holes or uneven roads? Had the impression that fatter tyres would absorb some of the vibration.. Head from someone who upgraded from 16 to 17 say that +- 80km per tank lesser after upgrading.. That's y I'm considering..

I think you need to take into consideration what type of 17inch rim and also the tyre profile used. if its within the tolerance, there should be no change in the speedometer reading and the FC. it will only meant that the 17inch/tyres set is much more heavier than the original 16inch/tyres set.

I don't think the FC reading is needs manual calibration due to different rim sizes. if you say resetting it by say 1) unplugging the car battery or 2) use the average of a few fuel tank refills, then it makes more sense. usually option 2 is more viable.