1. I think she is a cold-blooded murderer due to the fact that she was the one to devise the plan, and to clean the evidence to hide the actions that she and Macbeth had committed. Not only that, but she also pressured the honorable Macbeth to commit the crime and called him a coward if he didn't, provoking him. Lady Macbeth had every intention to see this murder of king Duncan to the end, thinking of a intricate plan of killing him, drugging his servants and have Macbeth kill them so all evidence will be gone.
2. She faints to hide the fact that she was involved with the murder of King Duncan and the fact that she was the one to devise the plan itself. Her fainting made it look like she couldn't handle the news and that she never knew what was going on, thus hiding what she did. It works in her favor because nobody suspected her, due to her acting and pretending to be surprised.
3. It was as if he lost it. Guilt of the murder overwhelmed him that he didn't even want to believe what he did, resulting his wife to call him a coward again because he didn't want to go back and finish the job of taking care of the evidence of the murder of King Duncan. He completely regretted it, even hoping that Duncan was still alive even though he was the one who took his life.
4. I believe that she wouldn't commit the murder is that she wants Macbeth to be cold hearted and strong so he can be king like she wants him to. She wants Macbeth to be able walk away and not feel guilty from this so that she can gain from Duncan's murder. And from the way shes forcing Macbeth to do the dirty deed, going as far as calling him a coward, it could be that she wants to gain from him being king, but if something went wrong, she wont be accounted and blamed for the king's murder because she wasn't the one who done the deed.
5. If he wants to stay as king, he either has two choices. Lay low, and hide the fact that he killed to king forever, and rule the kingdom as best as he can. The other option is him killing off whoever else is in line, and anyone who opposes him, as one, the next to be king such as the old king's sons could be heir to throne if people don't like macbeth, thus also getting rid of anyone who opposes him to allow himself to be king for a longer while.
