Gosh, I'm so sorry you are having such a hard time.
DS1 had reflux, but didn't get it until he was 6 months old. Nighttimes were hellish, until we started putting him in his carseat to sleep, being upright really seemed to help. It was cranial osteopathy that cured him in the end as the meds were making no difference.
Now, about a year and a half ago I got an excruciating pain in my stomach. It was a classic acid stomach, so not dissimilar to reflux, only the acid wasn't coming up into my osophegus. I was in tears with the pain. Zantac which is Ritadine I think was useless, but Losec worked a charm although it took 3 days to kick in. I was also on painkillers which helped. Ask your GP can you give him something for pain to see if that helps, you can get paracetemol suppositories which we use for dd.
I hsd several bouts of that pain over a year long period and after lots of negative tests for a stomach ulcer, I had food allergy testing which showed an intollerance to dairy. I have had no episodes of the stomach pain since I gave up dairy.
Would you think of trying soy formula? That fact that he was worse when you had dairy implies that he is sensitive to it, and often food intolerances go together so there may be something else in your diet that is affecting him, but pinpointing it is so hit and miss. I am loathe to suggest anyone should stop BF, but perhaps it would be worth trying.
The other thing that helped me when I was in pain was heat on the upper part of my stomach, high up under the ribs where the acid was burning. A hot water bottle or one of those cherry stone things you can microwave.
Thinking of you and hope you both get some relief soon, xx.