I do live in the EU, if the plan to get access to the phone number with the telecom operators on monday doesn't pan out I will try to do that.
Honestly I don't mind waiting weeks to recover the contents of my account as long as I know that it's not lost forever. But all the FAQ and comments on the internet regarding similar scenarios have no good ending and people just giving up with no recourse.
I knew about Subject Access Request but didn't cross my mind I could use it in my current scenario. Thank you!
That will get you back the contents of your account (emails, photos, etc).
You can also try submitting a right to rectification. They hold data about you (your account) but have incorrect data regarding ownership.
If either of those fails, you can escalate to the data protection authority in your jurisdiction.
It is likely to take several weeks though.