I would like an honest opinion about the PCB circuit I have designed
Designing a BLDC controller for high current motors is not an easy task, layout is very important and not only the polygon pours and which layer is top or middle. You have to focus on the switching traces, grounding , decoupling etc...

I donot claim that this is the best way to be done , but that is how i would do it anyway :


use middle layer1 as Vcc (50v) 
use middle layer2 as GND and donot use any other pours on any other layer for GND , anypoint should be connected to this plain by a via or via(s)
Use top layer and buttom layer for motor ( U , V , W ) traces and anything else. 
pay attention to the gate driver switching traces ( that feed mosfet gate) , make them as short and wide as possible. 


check those appnotes for more info :

AN-9005 Driving and Layout Design for Fast Switching

PCB-layout considerations
for nonisolated switching
power supplies