I think this is solved. I'll try to post the steps to perform it. I was right when i said this problem remains in file permissions.
As you can see in the previous log mysql try to start but it cannot read needed directories.
in the previous instalation, the directory structure was created by xampp script which, i guess, create an user "mysql" and assign the correct permissions. So the only thing to do is create this user and then, assign the ownership and permissions to the correct directories.
So.. first we extract the tar.gz file in /opt dir
then we create mysql user.
mysql must own these directories:
sudo chown -R mysql lampp/mysql/
sudo chown -R mysql lampp/var/mysql/
Now mysql service is running