I fixed the issue with the distortion modulation. It turned out that the issue wasn't so much that the modulation was "upside down" but that the volume attenuation wasn't needed and indeed a bit too much, bringing the volume down to near 0 as the modulation approached 1. It works properly with with that part removed completely.
While I was at it I made sure that static modulation amounts are always positive, as the results for negative amounts of modulation made no sense to me. Yours, Kas.
