Oh, my goodness, I have the EXACT same problem.
Wow you must be tired. Try having a family meeting at a neutral time, such as 2 in the afternoon or so. Explain that you want to help your son but you also need a good nights sleep to be the best that you can be. Ask him to help with ideas to keep him in his room. Write down all of his and your ideas with no judgement then read the list together asking your son if the ideas will work. This does not have to be serious. It can be fun and enlightening. If your son says sleep with all of the lights on you can talk about energy and the planet and ask him if that is the best idea offer up the idea of a night light or two. or put a picture of you in his room or...... see what he comes up with. you may be surprised.
I would love to hear how it goes.