Long thread, forgive me as I haven't read it.
Having just gone through this, I chased so many items, spent unnecessary amounts on new parts, only to find that a power wire directly to the battery fixed all my problems. I now have thousands of miles of confirmation under me.
To be fair, Electrosport advises this additional wire, and they were right. This probably would have fixed my charging problem even with all of the OEM parts as well.