the cover off if you like and see. it should be set at 1.
flushing. steam systems as a whole don't need to be flushed unless you are having water level problems. however, there should be a low water cutoff on the front of the boiler. some of those do need to be flushed, but to advise on that a if you could post a photo of the front of the boiler showing all the controls we can be more specific.
uneven heat. two steps. first, follow all the steam pipes out to the ends and see if they have main vents on them. they should. if they don't they're needed -- 