Maybe try the leave him for 1 minute then come back, leave for 2 mins come back, then 3, then 5, then 10 or so. Lets him know you are coming back. I would say whatever you do though, don't drop the guard and let them into your bed. Make sure everything is done in their bedroom and their bed. I'm not sure about the controlled crying, as its comfort being sought. Best of Luck with it... of course it may simply be just a phase as well..