You're correct about R2 of course. I didn't look carefully at the schematic and thought it went to ground, not the MOSFET gate.
You don't seem to have enough output capacitance to give a reasonable low ripple voltage. I got a reasonably stable output by changing C1 to 20µF, reducing the loop gain by changing R5 to 42kΩ, and rolling off the loop response by changing C4 to 1nF (Those are not optimum values since there is still some low-level oscillation in the inductor current). The output ripple was about 20mVpp with those values.
I used a soft-start time-constant of 0.6ms, which avoids any significant start-up overshoot.
Note that you should have a resistor in series with Q1's collector since there's noting to limit the current through the zener diode D2 when Q1 is ON. Something between 500Ω and 1kΩ should work.