Solution for limiting fire hydrant pressure
I think the only solution is to install a pressure relief valve between the distribution pipe and the hydrant, but you'll also need a manhole in order to be able to adjust the settings.
Actually, it would be possible to put a pressure stabilizer on the pipe that feeds the hydrant, but is there a risk of "clogging"? I ask because except when being used in cases of actual fire, the hydrant will only have occasional flow throughout the rest of the year during maintenance and testing.
Yes, that can happen, unless an operator opens it or it is put through a periodic flushing.