Getting my information from decades of owning motorcycles and learning all I could about them.
Return spring doesn't retract the piston & pads, it prevents the weight of the pedal from applying pressure on the master cylinder. The pedal has considerable leverage over the lever, so the pressure applied to the master cylinder would be several times the weight of the pedal. What the return spring does is to prevent the pedal from applying the brake; without it, it's like riding the brake all the time. With the power you have, I doubt you would notice the drag, but your brake components will wear more quickly and generate heat. Millions of motorcycles have a return spring and stop on the brake pedal (cars and trucks do, too). Just trying to be helpful. If you are happy with it as is, that's great.
https://www.google.com/search?q=mot...0MbVAhUDx2MKHY99D5oQ_AUICygC&biw=1680&bih=898
Kick start lever is probably the result of sloppy factory work. To get the lever all the way on, you will need to remove the pinch bolt, slide the lever in until the pinch bolt hole is aligned with the groove in the shaft, then reinstall the pinch bolt. The bolt sits in the shaft's groove so that the lever won't fall off if the bolt becomes loose.