Determining Phase Boost needed to Compensate SMPS
The phase boost in a type-2 compensator depends on the distance between the zero and the pole. If they are spread apart, the maximum boost goes up to 90° in theory while it goes back to zero when they are coincident. To determine the amount of boost, have a look at the below picture:



Boosting the phase actually means that you will tailor the compensator G so that its argument at the selected crossover frequency \$f_c\$ is less than -270°. These -270° are due to the pole at the origin (integrator) and the inverting op-amp which brings an additional 180° phase shift. In the example, the plant H argument at \$f_c\$ is -175°. Should you try to close the loop without boost at all with a simple integrator, you would end up with a total shift of -175° -270° = -360°-85°, showing a negative margin. 

What you want is a positive phase margin implying that the loop gain stays away from the -360° limit at the 0-dB crossover frequency. Selecting this margin depends on the transient response you want but assuming a 70° PM is your goal, then the sum of the plant argument and the newly-designed compensator must be -115°: you must boost the phase by -270° + boost = -115° implying a boost in phase of 155°. You will find more details in the APEC seminar but also in here with a comprehensive coverage of the subject.

Now coming back on your model, it is oversimplified to me as it does not include the sub-harmonic poles contribution. I would advantageously switch to the CM PWM switch model described extensively in Vorpérian's papers or in this APEC seminar.