Cannot create an appropriate regulation
I think there will be some problem with the calculation. For this to work without regulation, two things must be met.
1- The duty cycle of the switch signal is fixed.
ON time = 36 x K
OFF time = (260-36) x K ;(K = constant)
2- A minimum of inductance is required for the current of the inductance to be continuous.
That is, it cannot be decreased to zero during the switch off time.Here we choose either inductance or frequency. One defines the other.


The output capacitor only affects the ripple of the output signal. Its value is not critical.
I don't know where the 90 uH came from, it can't be ruled out in principle, but in practice it would require too high switching frequency.