I have a few thoughts on your questions. The mosquitos could be controled in a few ways.. if using a constant water flow it would reduce the likelyhood that they would even consider it as a place to procreate. Also with regular water changes (every couple weeks in most hydroponic systems) They will be less likely to take hold.
Another option is if you use bleach to get the chlorine levels similar to that of a pool. (I have been germinating my
seeds in a 10ppm+ bleach solution and they don't mind). I use a higher concentration for germinating because it tends to be stagnant water and more likely to become infested with various things than moving water.
If using bleach do not use H2O2 you will make salt water and nagate the purpose of adding either because they react with eachother.
Water conservation is a tricky question, because the amount of water in the res and if you use it as dump water or if you refine the water after use decides the conservation of it. Typically hydroponics is more water efficient than normal growing. The water is held away from the open air so it condences back into the system rather than floating off into the flow of air. Also the water change cycles will depend on your ability to maintain the quality of the
nutrients, as well as the size of the res. I think it was mentioned before lettuce typically uses 1/2 gal of nutrients a week (might be wrong on that one it is somewhere in the forums) So if you have a larger res and can maintain it's quality you can go longer before changes. If you use a smaller res you have to change more often because the plants use up the nutrients and you would be starving them of what they need.
On a side note about the polyester medium. I have been playing with a few varieties of it to see about the quilities as a medium.. The quilt batting is my favorite so far. The poly-fil for stuffed animals and pillows tends to be a thicker fiber and seems to wick very little. If using the poly-fil I would suggest a top drop from what I have seen so far... The quilt batting wicks nicely in comparison. I have some oregano and cilantro on a piece of batting and the oregano is starting to germinate with just the moisture that is wicking up from the edges of the batting that I have in the humidity dome. Not to mention the large surface area provided from the poly (the small pockets of air in the batting) lets the dew form all through it. I will make a thread with my findings on what I have tested so far and try to keep it updated as I find things.