Farmer-
You are a real thinker. You ask good questions.
Don't disregard "feelings." Those feelings, when we are doing what we are supposed to be doing and staying close to the Lord, can be prompting from the Holy Ghost. Sometimes we don't recognize them at the time. Some of the worst situations I have put myself into in life have been when I ignored small twinges that something wasn't quite right. The challenge in life is to learn to trust your feelings, one way or the other, and then have the power to act upon them. For myself, the most dangerous and devious thing Satan can do is to mimic good. As has been said before, there is a quiet, inner peace when things are right.
Thinking like Satan, how much better is it to be almost the best choice? Almost good? It is bad to go to the store on Sunday. But going to the park? Letting the children play at a friend's house on Sunday? Those things don't seem quite like sinning. But they inch us toward the gray line. I'm PTA President at my children's school. It is a good thing. But when I realized that I was spending so much time on PTA that my family was not getting the attention they needed, I had to admit that my priorities had shifted away from the most important thing. It is so easy to start heading toward the gray areas.
I myself don't think that Satan can imitate discernment. That quiet, sure peace that we have made the best choice is like no other.
Just my two cents.