A.L.
Sounds like he could be developing night terrors. I have had similar issues with my now 4 1/2 year old and I used to read her books related to what her current fear was- I sometimes added to the story or changed it to pertain more directly to her and her fear(s). Another thing I did was begin a new bedtime routine. A new routine really helped us and just talking out the fears helps to make it less scary.
If you feel he is genuinely afraid then I wouldn't let him cry it out. He needs you. But if you think he is learning a new behavior, putting off bedtime, etc. then crying it out could work if he knows what his expectation are and that you will not stay in the room if he is crying/acting out.
Hope that helps:)