Writeacher, I really need your help to check these sentences!! Too many mistakes.

1) Lady Macbeth compared the Duncan's murder with a painted devil, a picture that scared only children who thought it was real.
Correction: Lady compares dead and sleeping people to a painted devil (the image of a painted devil), who was used in popular stage performances to scare children.
2) So, at the same time, if Duncan was death, Macbeth didn't have any reason for being frightened.
As Duncan is dead, Macbeth has no reason to be frightened (of)
3) She told him to clean his hands and to take back the daggers to the crime scene. (She tells him to wash his hands clean and.....)

1. Lady compares dead and sleeping people to the image of a painted devil, which was used in popular stage performances to scare children.

("which" refers to the image, not the devil)

2. As Duncan is dead, Macbeth has no reason to be frightened.

3. She tells him to wash his hands clean and take the daggers back to the crime scene.
("back" needs to be moved closer to WHERE the daggers need to be taken -
an example of a "separable" phrasal verb: http://grammar.ccc.commnet.edu/grammar/phrasals.htm )