Please be a bit careful with Ritadine unless you are sure his/your B12 levels are healthy. It is a PPI drug & will therefore deplete B12 further - it made my own DD worse, thankfully she was at an age where she could communicate that, your DS isnt.
It took 13 yrs before we finally got a correct diagnosis for DD, her health got worse & worse over the years until she was very ill with a list of other diagnosis such as SPD, IBS, Colitis, Chronic Insomnia & a list of allergies & intollerances, she eventually ended up in a wheelchair.
Treatment with B12 injections has almost cured it all, including her soy allergy & she is walking again.
At this age we managed to treat the symptoms, reflux, poor sleep etc naturally, layered foods such as lettuce, onion etc caused colic, food additives, especially azo dyes, benzoate preservatives, MSG & artificial sweeteners all caused stomach trouble, including reflux as did lactose, soy & Cochinael - avoiding these & giving her "Golden Milk" which is a pleasant warm drink made from Turmeric, Almond or coconut milk, honey etc (google for a recipe) helped reduce symptoms too - the tips above with epsom salts etc helped her sleep