Won't the return flow from the booster pump act as a big resistance to the filter flow trying to get by the blast from the venturi output? I would expect to see the filter flow drop close to zero and the booster pump primarily recirculate the same water over and over. If you used an elbow similar to a "sanitary elbow", with the side passage entering almost parallel to the main flow it would work much, much better. The venturi line flow would actually boost the filter flow then.