I have TFO's in three of my Glocks and have never had an issue with any coming loose, as for dialing in these, I use a depth micrometer off each side of the rear sight to insure it is centered. This will cover you for any self defense situation. There are marks on the top of the slide at the rear sight that will put you close enough. Center the rear sight evenly between them.
Just because you know you're paranoid doesn't mean someones not out to get you.
Sub club #622
Certified Glock armorer