You may want to get in contact with a polling firm to find all that out. I do know the MoE on polls is usually mentioned somewhere, and it’s generally between 2–4%.
However, I’ve seen in the past few weeks a lot of Trump supporters starting to reject the polls because the polls are not showing results Trump supporters want to see. The polls are probably right. This happens with every losing candidate; they and their supporters get mad at the polls, calling them biased, saying they’re totally wrong, etc. Every losing campaign does this.
For your third point, I am not a Trump voter and never was, and will probably vote for Gary Johnson.