Lady Macduff is radically different from Lady Macbeth. She appears as the more traditional woman, one who is loyal and protective of her son and, despite her anger at her husband for leaving them to go to England, she is still the traditional wife and mother-figure. (See Act IV, scene ii.)
Lady Macbeth, on the other hand, is the nontraditional female - the one who has pushed and pushed her husband into the throne of Scotland. When she reads the letter from her husband about the prophecies of the witches (I, v), she makes a speech about fearing that her husband is too kind, "too full o'th' milk of human kindness" to actually fight his way to the throne. Later, in speaking to Macbeth about his hesitation in killing Duncan, she says she would rather have killed the child she nursed at her breast than to go back on what they have planned as far as killing Duncan to claim the throne. Lady Macbeth is painted as the epitome of the evil, unnatural female. She is characterized as being closer in nature to the witches than to a mortal woman like Lady Macduff.
With regards to your question #2, could you be more specific as to which scene you are asking about? Thanks!
Answer to Question 1: In "Macbeth" Shakespeare contrasts evil and good through two female characters - Lady Macbeth and Lady Macduff. Lady Macduff represents good. She is a God-fearing, woman loyal to her husband and believing in his sound judgement, even though she sometimes doubts him. Lady Macbeth is a representaion of evil. In Scene V of Act I, in which she is introduced, Lady Macbeth's lust for power is immediately uncovered as she plans a plot to murder King Duncan upon reading the letter her husband sent her. Lady Macbeth is ruthless and unstoppable in her drive for the throne.
Answer to Question 2: The restoration of Scotland begins in Scene III of Act IV when Malcom, Duncan's oldest son, and Macduff begin planning against Macbeth. Later in the same scene, Ross, a nobleman of Scotland, joins them in their plan. In Scene II Of Act V, Menteith, Caithness, Angus, and Lennox decide where to meet with their soldiers - in Birnam wood [forest]. In Scene IV, the noblemen of Scotland meet in the forest and move towards the castle where Macbeth is. The next few scenes portray the noblemen's fight against Macbeth for the crown. In the last scene, Macduff conquers Macbeth and Malcolm becomes king.
Hope this helps.