Hello @szpigel ,
As you already remarked in the linked post on Radiative processes included when using PAIRBREM, the photons you get in this problem are not originating from proton bremsstrahlung, but are rather secondaries from inelastic interactions, bremsstrahlung from delta-rays, … . A dedicated mgdraw.f routine (solliciting the usdraw subroutine) can help you clarify exactly how many pure proton bremsstrahlung photons you will obtain, if of course you are above the energy thresholds which are detailed in the post mentioned above. Let us know if you need more clarification!
Cheers!
Andreas