That's so funny about being afraid of the dark! I thought the same thing about my LO because we left a little light on for him a coupe nights in a row and when he woke up at night he just babbled instead of crying and put himself back to sleep, so maybe that's part of it.
I found when I was trying to extend my Lo A time, i ahd to start with the second one, so the one after his first morning nap, cause if he had a bad night it was hard to push that first one. Maybe you can try that? Slowly though, like 10-15 min at a time.
HTH.