I would be tempted to try a hypoallergenic formula... we don't have reflux here, but we do have some degree of intolerance to caesin protein in milk and I definitely did notice a slow reaction time... also worsening over time...
6.00pm - Feed and bed
9.00pm Feed
11.00pm - Feed
And the last few nights won't settle at all and wakes every 10-30mins and ends up in our bed.
Also this ^^ those night cluster feeds could be part of the issue (I assume they are boob)... that much in a short time could cause indigestion
He isn't hungry, it's just comfort... so might be best to try soothing in other ways for a couple of nights...