Why is Tom so conflicted in the scene in which he eavesdrops on Aunt Polly, Mrs. Harper, Mary, and Sid? Why do you think Tom kisses Aunt Polly and runs away without leaving the bark?

Tom feels terribly guilty because he has caused everyone so much worry..... particularly Aunt Polly. He kisses her because under that tough guy exterior..... he loves her.

His heart was full of pity for her. He took out his sycamore scroll and placed it by the candle. But something occurred to him, and he lingered considering. His face lighted with a happy solution of his thought; he put the bark hastily in his pocket. Then he bent over and kissed the faded lips, and straightway made his stealthy exit, latching the door behind him.