Would it be better to remove the intel gma Kexts that I have installed?
Then installing OS X from a distro disk (like the one you use), it is recommended to install only bare minimum of drivers (kexts; that is no VGA or Sound or LAN drivers). The idea is to get the system booting and then troubleshoot the rest.
If it's really occasional video editing (not something you do for living), then yes i5 should be enough. As for graphics, it depends on the applications used. Some require powerful GPU, some are more CPU oriented.