Well, I don't grow them indoors, but I have several big clumps of them out in the garden. In fact my garden helper and I cut down two huge 20ft. stems off two of the clumps this morning. The leaves do naturally tatter like that in the wind. Otherwise, the huge leaves act like sails in high winds and would break their stems. Bananas do the same. The burnt, browning edges could certainly be a result of too low humidity, or if on the tips could also be fertilizer burn.
I'd say your leaves are such a dark green color because the plant isn't getting enough light. Most likely as the light improves in spring, the color will also improve. The plant makes more chlorophyll (green stuff) in its leaves in winter to compensate for lower light levels.
You really can't give this plant too much water, although I wouldn't leave it with wet feet too often.
Also, be sure to ease back on the fertilizer in winter just because the plant surely slows down or stops growing depending upon how cool your area gets at night. Check the analysis of the fert you're using, that it has the three numbers the same (a "balanced" fert) or a lower middle number so as not to give the plant too much phosphorus outside of the blooming season. Deep green color can also be an indication of too much phosphorus that can be stored up in the plant.
