Changing the FD oil at every engine oil change is a great practice. There is so little oil in that FD and the gears chew it to pieces that changing it that often is a very wise thing to do. So many think that oil's only enemy is temperature and contaminants. But the shearing properties of gear trains due to the extreme pressures on the tooth contact faces as well as the gears slide off each other chops the long molecular chains that create viscosity into short chains and with it the viscosity and ability to lube high pressure surfaces is lost. Oil is cheap. The devices that they protect are expensive.
On your site glass, WN, Loctite 567 will seal the threads from leaking and still allow you to remove it for cleaning. It will also prevent it from backing out due to road vibes. Silicone will let you remove it as well. It's just harder to get off when you want to clean the surface to reseal. Wire brush works great for that.
2000 Ural Tourist
Before you say something stupid, always ask yourself, "What would Harpo say?".