This is a process that will take time. If he's had you this long, you just have to be patient, but consistant. You've done a great job by getting him out of your bed. The next step is on it's way! You've already realzied that by sitting next to him that works. So, start there and slowing transition to your ideal situation (book, prayers, kiss, and you leave for example). First, try moving from sitting on his bed to sitting next to his bed. Tell him you'll stay in his room as long as he stays in bed. If he gets out of bed, put in back in and leave the room. Next, a video monitor, works great! You can actually keep an eye on him. As soon as he gets out of bed, call from outside the room and say "get back in bed, please" He will probably be a little freaked out b/c you know he's out of bed and he didn't see you, but that's great! If he keeps getting out of bed, then you have to discipline him as if he kept doing something you asked him not do that wasn't involved in bedtime. While you are sitting in the room, you can transitiont his way...I'm going to sit until you fall asleep...then after a few nights you can bring a timer and say "I'm going to stay for 20 minutes", then shorten the time each night, and, before long, you'll be able to leave after the last kiss! Once you get it worked out, the key is to be consistant!
Good luck!