Xecure
I think we need to take a step back and start again.
1. On the running system, where you log in as root, when you installed antiX using the antiX installer, you created a new user account. Can you log in to it from the terminal (instead of to the root account)?
2. If instead of starting the graphical interface from the terminal, you do
sudo service slim restart
Does the slim log-in screen come up?
3. Could you check if there is any /etc/X11/xorg.conf file on your system? And anything in /etc/X11/xorg.conf.d related to radeon?
Make a backup of these files somewhere and see if removing them will then permit autostart of the graphical interface. If not, you can move them back to their original place.
antiX Live system enthusiast.
General Live Boot Parameters for antiX.