What's the volume of your chamber and what's your pump size? The same flux can generate very different pressures.

But anyway, you can just try that with a pumped module without the RF power on, I think that's faster and more reliable.

Article Characterization of hydrogenated amorphous silicon thin film...

you can introduce hydrogen once plasma stabilize with Ar in RF mode with little amount and see the behavior like wise increase up to the insight derived from literature study...then characterize the results and optimize the ratio of Ar: H2...optimize working pressure too.