Before i would devote anymore time or money (for that matter) trying to reduce the hammer i would find the cause of the hammer.
Personally i would look at the filter first and the meter second.
I have no doubt that the work that you have done behind the plumber did anything but improve the quality of the install so we can rule that out.
The filter may be momentarily impeading flow. You may not be seeing this at the gauges as it may be too slight.
The meter should be tested by the purveyor at your request.
If all else fails you could install a flow/pressure loop near the meter and use a data logger to help diagnose the system.
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