The temp is ok but it could come down 5 to 10 degrees. Just open the door a bit each day if you can. Get some type of hygrometer, they're only 4 bucks at home depot. Humidity should be 60 to 65 %. If its too high, open the door or put a dehumidifier in. If too low, put a couple full cups of water inside and close the door.

The soil is fine and your mix is cool. The lights are good too as long as they aren't too close and drying out the soil. Def do an 18/6 time schedule. Put the six hours sometime in the night when you don't turn lights on so you won't have to worry about light leaks.

Spraying the soil is good and all but I think we may have stumbled on your problem. Spraying the soil gets the top, but what people don't understand is the seed is growing down as well. You need to get water at least halfway down the container when sprouting. But you can spray the top as well if you just want to pour around where the seed is. It will penetrate and you don't have to worry about washing them away.