I think you really have to force a schedule. It has to start somewhere, and you have to be very determined and devoted to keeping that schedule.
Every evening, after dinner and bath and all of that, play some soft music, no singing (singing might stimulate him), in his room, and read him a story, making sure he can see the pictures in the book. Tell him that he is a big boy, and you need him to help you with the story. Ask him about things you see in the illustrations. Have him ask you questions. Once you have read several books together, you can let him pick out his favorites each night.
Not only will this get him into a habit of being in his own bed, but you will give him one of the most wonderful gifts a child can receive...the love of reading!
After the story is over, turn the lights down a bit, and sit with him for 10 minutes. No longer, no less. 10 minutes. Or you can choose your own time limit, but always stick to it.
It is going to definitely take a few weeks to get him into this. You must be dedicated to it, or it will fail. You don't want to miss even one night doing all of the same steps. Children that age are comforted by routine, and once it is a routine, it is familiar, and less frightening.
Please stick with some type of schedule, and if your husband won't agree to it, tell him that he will be the one who has to 'deal' with your son every night. This worked great with my kids.
Hope this helps a little.