You've done a masterful job. Don't sweat the small stuff , 'till you get to the engraving part. A 15 " Crescent or pipe wrench will aid in lining up the flats. Tighten the plug in and out a time or two ,should fit ,ok. You also don't need a 1/2 " web of metal below and behind the lug face. The long lug takes more tedious inletting time. When ya get the plug installed , turn the barrel / with plug installed upside down , and trim 1/8 " off the rear of the lug and file the saw marks smooth. I second the motion to polish the breech face. It stays shiny for a while. and you will be amazed how the inside of the bore can be seen w/ just a flashlight.