I connected it to the second port and booted it up, then started playing around with the config again. Lo and behold, hdmi_group=1 didn't cause a catastrophic error! The rest was cake, thanks to you guys.
Very much appreciated, thank you so much for all your help!
Good to know. I tried a handful of games a while back and didn't have any luck myself, but it makes sense that some of the less demanding games would be playable. What kind of frame rates were you getting?