How Tight Should I Make This?

I was doing some biannual maintenance on my R2 and found that the lever with the spring on it (on the extruder which feeds the filament in - I don't know the formal word for it) was loose. Loose enough that that entire assembly could sort of angle off. The screw that is circled in faint yellow was fairly loose, but I don't know exactly how much it should be tightened. Tightening this screw did solve the problem, but also made it more difficult to depress that button.

Does anyone have any suggestions for this? Should I prevent this from happening again with some blue loctite?