Thank you for your reply kf2qd. I have mechanical reverse, so only one motor-direction is needed. The commercial controllers I have found, that are capable of the current needed, are too expensive for me, so I would like to take my changes with my simple mosfet circuit, if at all possible.
I have manipulated timer1 for PWM frequency of 31khz.
Would a 20A 100V SCHOTTKY DIODE be a good choice for flyback protection instead of 1N4004?