1. As to set up sqm, the unit is square meter. If you change the area, the water usage will be different. Netro uses the area and depth flow rate(inch/hour) to calculate the water usage. When the sprinkler system is professionally designed and installed, the zone is usually covered evenly, which means the large the zone is, the more sprinkler heads it needs. So the equation we use is Area(inch^2) x depth flow rate (inch/hour) x time (hour) = water usage(inch^3)
2. Yes you could set your zone with customized mode. To adjust smart watering, please go to settings->zones->select a zone->smart zone and choose your preferred watering mode. You can choose "customized" mode to adjust watering by providing the preferred moisture level and flow rate of your sprinklers.
3. We plan to sell on Amazon. it in the second half of 2020. Currently you can buy Whisperer sensors on our website and the delivery time takes about on week. Free shipping on orders over $ 150.