Which characters seem to find the Puritan way of life difficult?And which ones didn't?
I think the characters who have power in the play (Parris, Danforth) have no problem with the Puritan way of life. But they are not the only ones. I would argue that Elizabeth Proctor would not have had any problem with the Puritan way of life if she had not been placed in a bad situation. She seems to have been a very sober, godly woman who just got caught up in the witch hunts because of her husband and Abigail.
To me, the most obvious person who has a hard time being a Puritan is John Proctor. It's not so much that he has a trouble with lust -- to me his big problem is his desire to be independent. I think he is too unwilling to let his life be monitored by the minister, etc, to be a good Puritan.
In looking at the characters in the play "The Crucible" the characters that I see have the most difficult adjustment to the Puritan way of life are John Proctor and Abigail. However, most of the people who were prosecuted by Danforth and Paris have had a very hard time dealing with being Puritans under their misguided attempts to be Godly.
Abigail is selfish and manipulative. She is also non-virtuous. An expected trait of a Puritan woman is virtue and honesty. She exhibits neither trait. John succumbs to his lustful nature with Abigail.
Reverand Hale and Elizabeth Proctor are good people. Although we first think that Hale is on a witch hunt and will not judge fairly, he demonstrates an understanding of what is truth ad what is not. Goody Proctor is everything one would expect in a Puritan woman, but is accused as being a witch.