Let me get this straight, The rifle runs, does not short stroke, and has no problem, So since it's not broke, your going to fix it!!!!!!
The gas tube will leak at the sight tower. The part is held in by a roll pin, not screwed in with a gasket or sealer. The system was designed to have leaks due to wear. If the only reason that your are replacing parts is due to the leak, guess what, the new gas tube will leak just as much.
Also, I see that you didn't post about the leak at the back of the bolt, or around the carrier key to gas tube. I guess you missed these areas.
Ok, now that I have that out of my system, Just leave the parts alone. All AR rifles will leak from the gas block around the gas tube. The ones that are not leaking are just fouled/crapped up and will be the problem child when it comes time to remove the gas tube. Be happy knowing that when it comes time to remove the gas tube, you will not need to use a pair of vise grips, bench vise and a blow torch just to get the tube off.
Hope this helps.