Sorry to hear things have not improved yet. Hope the homeopathic remedy gets there soon, and helps a bit. Until then, I have to agree with going to see someone for alternative therapies, and look into food allergy testing. I know you said he would likely have a problem with someone he sees as being a doctor, but if you think you both could handle it, I would try it.
DS has reflux and is MPI, so I have been trying a lot of different things to see if they help. Our experiences:
Acupuncturist -I took DS to one when he was about 7 months old, and she used 1 needle (but asked me beforehand if it was okay, and I agreed). For the rest of the appointment, she did cupping and acupressure.
Cranio sacral therapist - does seem to help a bit with his sleep. He just explores her room or plays, and she follows him around while she works on him. He sees it as more of a play session than an appointment.
Naturopath - I recently went to see one for both DS and I for sleep issues. She suggested a diet change for both of us, pro-biotics, and suggested we both take flaxseed oil every evening. For me she also suggested calcium/magnesium supplements, which apparently can help promote sleep, and B vitamins to help with the stress. Of course these suggestions are from our medical histories, but I am just throwing ideas out there.
I would also suggest a chiropractor (can't remember if you have been to see one). DS had a bone behind his right ear out, which was putting pressure on a nerve back there, and made it harder for him to sleep. It improved things slightly when he got adjusted.
Hoping for a sleep study for you!