I highly recommend a paed. Contact RISA - reflux infants support association and see if they can recommend a good paed in your area who understand that silent reflux is a 'thing'.
I know you can hear horror stories, but some are very real even though they're very uncommon. What dose of reflux meds is he on? Both of my kids were on 10 mg of nexium 2 times a day.
What are his poos like? I'm wondering if it's possible that he may have a cows milk protein intolerance. That was the cause of both my kids reflux.
Big hugs. It's tough going.