Family link location and gmail

Hello,

I use Family Link as parental control and until now I was very happy with it, but I am facing 3 problems:

1- My son's tablet is locked and the parental code is not accepted. It says "this device is locked because the account '...' was deleted without the authorization of a parent of the child." However, it's impossible that the address was removed.
2- How to add two Gmail emails because the app seems to only accept one, but there might be a way to do it since my son needs access to his personal mail and his school mail.
3- My son installed an app that requires location to be enabled. However, when I enable location from my parent account, it shows on his phone that he cannot enable location services. I have the impression that I activated location to know where he is on my side in the app, but that it cannot be enabled on his phone so that he can be located for GPS or other purposes. Does the location feature exist with Family Link?
Thank you in advance.