Second, I tried many ways to change tomcat port to 80 instead 8080, but nothing that I tried really works at all.
So, I decided install Alfresco again and I chose the port 80 on instalation and problem solved (almost).
Now I decided to configure my DNS to point to my tomcat instalation, everything seems right but when I try to upload a file in Share, it fails. But when I do the upload in Share using the IP adress, it works.