Don't use any ferts the first 3 weeks. Dehumidifier water ain't that good because the grill it condenses on may be very dirty or have bacteria, thus making the water dirty.

Your fert should be fine once your plant is large enough to use it, just follow directions and slowly work your way up to full strength. It generally better to spend 20 bucks on a fert made for cannabis if your a newb.

Seed was formed from one pollen grain falling onto a flower. Pollen came from male flower somewhere. It could be from a Hermie, male plant, or rouge pollen in air.
Better to plant at least 4 seeds to guarantee 1 good female, two females are better. Its got a 50-50 chance unless it came from a Hermie then it has a better chance of being a female.

Good luck,