a safe and qualitative peq mode (see enriched when possible with some bands) and a possible export in rew format of the raw data of the chirp "wiim" would be a priority...Unfortunately that didn't help much, RC algorithm made some unfortunate decisions when calculating the filters.
Perhaps try to change Max Gain to 6dB and re-run RC. If that doesn't help then I guess you'd either have to accept the response dip or try alternative subwoofer positions.