I agree with Russell and David: toss the N-channel FET and use a P-channel instead. The IRF9530 looks OK if we keep an eye on the gate voltage, that should be less than 20 V, and since you have 32 V in that means you can't pull the gate all the way to ground.
Drive an NPN transistor or N-channel FET with the rectangle wave, and connect collector/drain via a resistor divider to the +32 V. 10 kΩ on the +32 V side and 10 kΩ on the low side will give you 16 V gate voltage when on, and a few mV when off. 16 V is good for more than 10 A. For Q1 you can use a BC546, for example.
You'll have to adjust the duty cycle of the rectangle wave to 16 %. Keep in mind that this is a DC/DC converter, but not a regulator: the output voltage will vary with varying input voltage. A next step may be to add feedback from the output voltage so that the duty cycle can vary to keep the output voltage constant.
I changed a few components' values after Russell's comment. Total gate capacitance of the IRF9530 is about 3.6 nF, and with the original 10 kΩ resistors this gave a charge/discharge time constant of 18 µs, which is much too slow for a 100 kHz clock. With the current 100 Ω resistors this is 180 ns.
C1 gives a short base current peak to start charging the gate faster. This wasn't required with the 10 kΩ resistors, as Q1 would be in saturation quickly, but with the lower load extra base current is welcome.