When you say you are not getting help from the OT - can you explain that more? Do you mean she doesn't work well with him, or doesn't understand his issues or that so far you've not seen the results you'd hoped regarding food and behavior? If she is not treating him kindly and respectfully I would find a new OT. If she is working with him in a professional way but you are just not having the results you'd hoped for, I would consider seeking out some additional support , like Floortime or DIR or Play therapy for the behavior and social stuff and a DAN doctor or other naturally minded doctor to help with the food stuff. Most kids with really limited diets like that have nutritional deficiencies and food sensitivities i.e. certain foods are causing intestinal problems which then spirals into other areas of development.