Several members answered your first two questions, but not that many focused on this one.
There are no elections for merit sources. What I mean is, there isn't a voting system where you have candidates and you vote for those who should have that responsibility. We don't know what happens in the staff quarters, but I doubt they have a voting system there. Perhaps they talk about it like "I am going to make X, Y, Z new merit sources, do you guys agree?", but I don't think there is more than that.

Even though there aren't elections, you have probably noticed threads with merit source applications. Trusted members can apply to become merit sources and then everyone is free to share their opinion about it. The admins could look at that feedback before deciding YES or NO if they want to.