Hey there bud. I just went through and read the entire thread. I think you are overwatering and it's dampening off and/or just rotting your seed/seedling. It looks too wet to me in every pic I see. After it spouts above soil, take the plastic away. Did you pre-water your pot before planting? If you did I barely mist at all for days unless it's just really dry. That's what I do.
Also, I think you're just over-thinking it all. Which is totally common as a new guy. Hell I still do it sometimes.
So hold off on all the spraying and take that plastic off and forget about it for at least 24 hours.