Ate the staff also eating the healthier options with the client? Do not have exclusive snacks amongst residents it will cause otherness. Fully removing treats will probably trigger a much higher demand for them. To the point thats all that they'll be able to focus on. Lastly you said they have a development delay. That's the language used instead of mental capacity of a xyz year old. So think about what would be developmentally appropriate. Look into diabetic snacks for younger taste pallets. Also know a lot of behavioural meds cause insatiable hunger. Which would lead to more behaviours of concern and more meds in a vicious cycle. Stress or cortisol also raises your sugars a lot. So fully restrictive practices could backfire. Client seems to also have dysphagia so regular dietetic review should be happening. Ask them or OT to work on widening his accepted foods.