Re: Default folder perms for other.
Your problem does not make sense (to me). In general, if a user is able to create files in the directory /var/www, that user should also be able to delete the files that he/she created. So are you talking about one user that creates files and another user that needs to be able to delete them?
Have you considered
In fact what i need is www-data user to have full perms in that folder and every new folder and file inside the root folder.
That should allow users in the group www-data to do what you want. An alternative can be setfacl which allows more fine-grained control without changing the original permissions.
chgrp www-data /var/www
chmod 775 /var/www
If you don't make backups of your important data, your data is obviously not important to you.