A question about dose rates

I have most recently been using G4 to measure the dose rate parameters of our newly designed radioactive sources, but now I am having some problems with the dose rate measurements.

We designed the I-125 radioactive source activity of 0.5mCi, according to the formula this 0.5mCi radioactive source can produce 1.85*10E8 decays per second. I used G4 with/run/beamOn 185 , 1850 and 18500 particles respectively.

And counting the absorbed doses in SD, I found that these absorbed doses basically showed a linear relationship. So I used the command /run/beamOn 185000 in the final experiment and multiplied the absorbed dose by 1000 to get the absorbed dose of 5mCi I-125 in the detector in one second.

But I don’t know if this method of mine is feasible, so I would like to ask for your advice. Also I have another question.

I see more in some papers that use MCNP to calculate absorbed dose, they use MCNP *f4 tally to calculate energy fluence (MeV/cm2) and then use mass-energy absorption coefficients to convert energy fluence to absorbed dose rate.

According to my understanding, I count the absorbed dose of SD in one second in G4, so that I can get the absorbed dose rate in Gy/s, and then I multiply this value by 3600 to get the absorbed dose rate in Gy/h.

Based on the above description my questions are as follows:

The first question is whether I can conclude that G4 shows a linear relationship when counting the absorbed dose, such that I can use the command /run/beamOn 185000000 instead of /run/beamOn 185000 or even less and multiply it by the corresponding multiplier.The resulting absorbed dose rate of SD in one second was obtained.

The second question is whether the way I calculated the absorbed dose rate using G4 is correct, which is to first derive Gy/s and then multiply by 3600 to get Gy/h.

The third question is whether there is a big difference between the absorbed dose rate calculation method of MCNP and the absorbed dose rate counted by G4. If my absorbed dose rate calculation method is correct is it possible that there is not much error between these two.

Thank you all for your responses.