Hey MaJFisssh,
It sounds like you're now aware, but just to clarify - unlinking a platform from your EA account does not allow you to transfer that progress to a different EA account. This can cause a permanent loss of progress, but re-linking your Xbox account to its original EA account as you've mentioned would be the only way to try recovering that progress.
We are not able to manually recover anything lost due to unlinking, so getting those original accounts re-linked to see what may be automatically restored would be the best bet. If you're unable to get your Xbox account linked to that prior EA account, you can contact support directly so they can take a look at getting those re-linked with you.