With that size of motor the controller will have to be at least 30A continuous rating, meaning that, yes, it will be 50-60A max.
If you get a battery that is capable of delivering 50A max it will be too little. To avoid heat stress and buggering it up within about a year, you need a battery capable of delivering 10-20% more current than your maximum controller rating. This means something in the region of 66-70A.
This is before considering the actual capacity of the battery.
What you are actually talking about is a motor bike with bicycle brakes and frame, that were never designed to take the weight and stresses you are about to impose on them.
Why not just buy a motorbike and be legal?