John Proctor is the tragic hero because he is pulled into the histeria due to a past action. In the play he says to Elizabeth it has been cold ever since (the affair he means) and he wants to fix his marriage but it is hard. The witch hunts give Abbigail a way to try and get rid of Elizabeth. Abbigail is cunning and nefarious (wickedly evil), she uses the "out of body" experiences, needle prick and the poppet that Mary Warren made, and fear to further drive a wedge between John and Elizabeth. Despite all the mess surrounding the witch hunts John still tries to protect his family. He stands up for his wife, refuses to sign a confession because that will be all this children will have left, and if he had not tried so hard to disprove the girls scheme Reverand Paris would have believed them to the end. Evidence of heroic actions are present in the text of when changes occur.Abbigails antics brought John and Elizabeth back together just before he was to be hung. Bitter sweet end for a family man just trying to save his wifes life and family name. Email me if you need or want more details. I loved the play and my history/english teacher spent a week going into the details of it. I could pull out my old notes for you. You'll do great on the essay!
A side note for a great paper: Keep your thesis strong and consise. Don't veer off and get vague through out your body paragraphs. Use textual support right, over doing it makes a paper weak and confusing if you use the wrong text in comparison. Remember that if you are having trouble staying on your thesis play with it a little to work with your details, that is easier to change than rewriting the whole paper.