Sunlight is generally a bad thing for an aquarium. It is a major contributor to algae blooms in an aquarium.
As for the light the 50/50 bulb will be fine. Without upgrading the light fixture itself you will be able to grow crypts, bolbitis, anubias, java fern, and java moss.
"The simplest explanation for some phenomenon is more likely to be accurate than more complicated explanations." -Occam's razor