Sorry for late reply.
i will be available from now.
about my solution to update to latest version i think you missed no.2 (Use a mysql backup copy where you never updated to latest version. If you update to 10.x version then role back, it may fail update. So ensure you never updater to 10.x version in that backup.) because before 10.x version some tables you mentioned never used.
Please confirm if you have ever updated to latest version in that backup. If you updated to 10.x version then again role back to 8.x version then there need some extra step and code. I will give you. Please let me know.
Please check FEP_admin_options
and fep_db_version
option in db (do not change manually). in FEP_admin_options you will get version in serialized array. Please let me know both.