Hello Federico. The migrating error should have been fixed in 1.4.3, please try to run it again using version 1.4.3.. If that is still not possible, the whole migration indicates that you used a VERY old version of Trinity, and should then not be affected of the exploit that came in 1.2.X versions.
Please read https://medium.com//how-to-check-your-balance-without-using-trinity-e1cac78e97a7 for how to lookup your funds without using Trinity.
Also, beware of scammers lurking around this space. Never share your seed with ANYONE.
If it still doesnt work after trying to migrate again with 1.4.3, please make sure you have your seeds backed up, then reset the wallet. This you can do from Advanced settings.
t00k, Discord Moderator. Not part of IF.