A few drops should not kill anything, provided it's not short circuiting anything and it's dried before any damage/erosion occurs.
The data is actually not looking that bad. I am sure it's just a matter of fine tuning the position of the sensor so it has a more ideal path to the water surface. It works with ultrasound so if it bounces in a weird way from the inside of the sump well (walls, the pump itself or whatever else) it might throw the readings off like that. This happens to me sometimes when I recharge the unit and need to reposition it, takes a little fiddling to get it right.