Pressuretrol and Radiators

RobLC

We have steam heat made by natural gas.

Keyspan comes once a year to clean out the pigtail on the pressuretrol. Then the heat works fine. If the pigtail keeps clogging, is it wise to get a new, clean pigtail?

If the pigtail keeps clogging, would that damage the pressuretrol itself?

On the top of the Honeywell pressuretrol there is a screw (not the cut-out) threaded through a spring. Is there a finely calibrated setting for it?

We have a total of 16 rooms distributed over 3 floors.
Three of the rooms on the second floor are not used in the winter. Can we close the supply valve at those three radiators, close them completely and close the doors and expect to see some decrease in fuel bill?

Your advice, help, and time is greatly appreciated.

Many, many thanks,

Robert