I hope you have resolved your problem with the regulator by now. I know it must be vary frustrating to not be able to do what you want to do. At least you gave me an excuse to go down into my basement and check my keezer. I went ahead and poured a Cross Roads Pale Ale while I was down there. I have six regulators in it from Micro Matic. I looked at the paperwork and they are discribed as Economy Standard Regulator. They are bright red in color with the gauge on top and the exact configuration you are describing as far as the connections go. At this time, I have all of my regulators in a dazy chain connected to each other, so that I can feed from one CO2 tank. The Micro Matic has a threaded plug on the left side which uses an allen wrench to remove the plug. It rotates in a counter clockwise direction in order to remove plug. You may have to mount the regulator to something solid, so that you can apply the necessary force to release the plug. Hopefully you have the proper sized allen wrench, so that the plug does not get stripped. It is a rather large one. I keep it right inside the lip of my keezer, unfortunately I do not know the size. Do you have a vice grip set of plires. If not, you may want to invest into one. Attach the vice grip plires to your allen vary snugly. This will enable you to apply enough force to break the threaded plug loose from the regulator. Cross you toes, because you are going to need your fingers. Apply counter clockwise pressure. That's it, vary simple.
Again I do hope you have already solved your problem and moving on to bigger and better things.