At least you see here:
that
just works.
KMS is disabled on the kernel and the intel driver will not load even if xorg calls for it.
I would suggest to boot the ISO by adding:
systemd.unit=multi-user.target
to the kernel parameter and let the other parameters be default. It will stop at the basic non-graphical login. There you can login with manjaro:manjaro. If until there everything is ok, you can try starting the display manager:
sudo systemctl start display-manager
If the signal is lost again, you can try to switch to another TTY:
and stop it:
sudo systemctl stop display-manager
and have a look at the journal:
journalctl --unit=display-manager
or the xorg log:
cat /var/log/Xorg.0.log | less
Please let me know if the non-graphical login works 