I have gotten a hold on the algae. The actinic light is still on, so I'm inclined to believe that it's not as big of a culprit in algae growth as is rumored. My lighting is cut back considerably now, though, with only the one 54W actinic bulb (for it's color-effects) and the one 10000k 54W HO bulb. What is amazing to me is that since I cut back the lighting to this extreme, my once suffering amazon sword has sent up dozens of new leaves. They're bright green and strong. AFTER these leaves began to surface, I cut back all of the old algae coated leaves. I'm just really shocked at how well everything is doing (knock on wood) since I cut back the light.
I will get a proper test kit and proper ferts as soon as I can get to town (probably next weekend). For now, here are my numbers with the inaccurate test strips.
Since last week, everything has remained constant except for pH which dropped 1 point from 9.0 to 8.0 and Nitrates which dropped from 80 to 40.
Also, I realized I hadn't yet mentioned something that could be important to my dying fish issue - my tank is fairly brackish, because my mollies and halfbeaks are the main attraction for me, and black mollies are prone to ich and fungus which salt wards off. All of my guppies are now dead, but everyone else is thriving. This means I no longer seem to have a problem, because no one has died since last week, and my black mollies had a bunch of healthy babies over the weekend who are thriving.
Oddly enough, my neons are also thriving, and I've heard they are very sensitive and intolerant to salt. Could the salt have killed my guppies, swords, and otto cats and yet left my neons unharmed?
As for the CO2, based on everyone's comments I've decided to hold off, and go back to trying the low-tech plant setup. At least for now.