If the ultimate goal is binaural without headtracking, I would bypass Ambisonic encoding altogether and use a binaural panner. One that works well for me is the Sennheiser AMBEO Orbit.
If that still doesn’t “work” for you, then you’ve probably hit the limit of binaural stereo: if the HRTF used by the binaural panner is too different from your own ears and head, the results will always be disappointing for you. But maybe not for somebody else…