Hi,
I understand how important your Realm world is, especially since your subscription is still active.
Based on your description, it seems you’ve already tried several troubleshooting steps without success, so since this issue is related to Minecraft, your best next step is to contact Minecraft support directly so they can check this for you:
https://help.minecraft.net/hc/en-us/requests/new?ticket_form_id=360001225811