I believe that you are already well above the level of sophistication of typical DIY project (electric or gasoline) in this analysis. Looks good to me.
I would add that in addition to illustrating the top speed, the available power in excess of the power required to overcome the calculated resistance is the power available to accelerate.
I would add that in addition to illustrating the top speed, the available power in excess of the power required to overcome the calculated resistance is the power available to accelerate.