Hypoallergenic is basically nomenclature. If a hypoallergenic food contains beef, and your dog is intolerant of our allergic to beef, he’ll still produce a response.
You wanted low residue. Did you identify your dog’s reaction to foods of varying fiber levels? The food you’re feeding now contains a lot of grain (filler ingredient), so it’s producing a larger stool volume.
I’d look for a grain free food with a higher percentage of meat protein and lower carbs along with lower fiber. You might look for Victor GF Ultra Pro, which meets those criteria and has a fiber level of about 2.5%.
I’d also consider adding digestive enzymes. One I’ve had great success with four one of my dogs is Swanson’s BioCore:https://www.swansonvitamins.com/swanson-ultra-biocore-optimum-complete-ultimate-full-spectrum-enzymes-90-veg-caps. It helps him break down sugars from starches and vegetables better than any other enzyme I’ve used.
