Since he was struggling in what he was doing, such as placing the stone in it's place and that it was not perfect and was just partial. Shows that he was worrying. Also because the hair on his arms were standing up, it showed that he was stressed and scared because of Fortunato's odd response. I hope this is correct!
The noun "herself" is a intensive pronoun. Since you can take out the pronoun and the sentence still makes sense that means its intensive. Hope that helps!
