No so feedback, the output voltage will heavily change with load.
Why the gate potentiometer? If that's your workaround to reduce the output, its totally wrong, you must adjust the PWM duty not the mosfet condictivity.
As they already told you, the proper circuit for this is the TL494 / KA7500.
If it wasn't stable, it problably was due a poor circuit design. Specially with flying wires like that.
A TL431 might do the job. Add a optocoupler to provide isolation. Adjust the ref pin resistors to limit the voltage.
