Hi, welcome to the forum, inadequate sleep in night has consequences which include daytime sleepiness and fatigue, reduced alertness, and compromised performance in specific neurobehavioral domains.
Children today are subjected to violence, illicit behaviors, Video games, violent and unrestricted television programs and illicit music which are leading to nervous conditions in children who in turn suffer insomnia. Environment and climatic changes are also some insomnia causes, since chemicals and pollutions are surrounding our world and causing insomnia.
If your child spends long times looking at the TV, listening to music or playing video games, loud music etc then this is going to affect the nerves, and your child is not growing properly and insomnia most likely will continue in your child’s life.
Also as a parent you need to convince in the way he understands and why he wants you to sleep early before him. You need to talk with him freely and understand of what he is thinking. Also you can remove the women poster of which he is scared.
You need to convince him for daily exercise, watching good movies, restrict the video games, loud music etc. With this you need to make his room silent without any disturbance, give warm bath before sleep, avoid day sleeping, make him physically tired by jogging or exercise so at the end of the day he sleep due to tiredness and maintain healthy diet.
Use anger appropriately, Give firm instruction and direction, and Give plenty of affection to kids so they listen you.
I suggest you to consult physician. Take care and regards.
I think its just a matter of him feeling spooked to be the only one awake in the house at night. I thinks its just a kid phase, cause I have heard of lots of my friends kids going through this. When one of my own kids went through it, I dealt with it by making sure they were in bed, lights out a couple hours earlier than when we would go. Then I just played up the (I have to be up extra late tonight, so dont worry you will have plenty of time to fall asleep)---remember--no lights, no tv, no music. It worked. Also, make sure he is not watching things that may be scary (the news, sci-fi, etc...)
How about continuing the reassurance but attempting some Behavioral therapy techniques. Instead of focusing on why he is feeling the way the way he is, there are simple steps you could at least try. I'm not saying the way he feels is irrelevant by any means, it's very important. It seems though that he is comfortable communicating with you, telling you how he feels. You have tried to address the issue from this perspective but now he is confused about the why, but the behavior continues.
Your reassurance should no longer focus on why he shouldn't be scared or worried, but why his falling asleep first changes nothing. Focus on the fact that you would wake up in a second if he needed you. I don't know if you are just down the hall and you can hear him, or if he has to come to you, but either way, whether you are asleep or not does not matter as long as he has access to you.
Use basic reinforcement in efforts to bring about change. He is 12 years old, there must be a ton of things he wants ranging from video games, to ipods, to taking karate lessons, whatever it may be......Come up with an arrangement, that when it's time to go to bed he goes up and stays there. He does not leave to come check if you are awake or not. You can add reassurance by saying in the beginning you will be peaking in, not to talk, but to make sure he's keeping his end of the bargain. Tell him he may not even notice it but you are checking.
Again this is just a basic outline you can come out up the specifics if you try it out.
You can arrange a system with one big reward after a decent period of time (a computer, ipod, whatever he has been asking for), or smaller daily rewards such (I don't know his favorite food, candy, baseball cards whatever.)
The key is that you both stick to the deal, there can be no leniency on that or it will fail. Obviously if he wakes up at 1am freaked out and needs you, he still kept his part of the deal. The point is getting him to fall asleep on his own without certainty of whether you are awake or not.
Address all concerns, and use reinforcement. It really should work. I wish you the best, hope this helped.