1. Is it possible to have more than two Master Files active at once?

2. What is the purpose of the Keywords tab?

3. Where are the Amulets of the Divines in the CK?

1. Yes. You have to enable it in the CK ini file. Google is your friend on this.

2. Key words are used to group things together. IE when wearing a full set of glass armor, sometimes guards will comment on it. They do this via keywords attached to the armor. Or, you could have a set of weapons with the keyword "Taco", and you could make a quest that at some point curses all weapons with the keyword "taco" to have -50% damage for the duration of the quest.

3. The Objects window has a filter on the top. And at the bottom of the list is an "all" option. Type in the name of the ammulet, or a word like "mara", then click the "all" section and it will filter out anything not matching what you typed. If you can find one, you can find them all fairly easily based on the file structure of the first.

3. Filter for Religious, their under Items -> Armor