Can someone help me with a third point concerning the "significance of sleep and the lack of sleep within the play of 'Macbeth'"?When writing an...

With Macbeth, conscience does seem to enter into the equation.  For, just as Brutus sees the ghost of Caesar in "Julius Caesar," after having assassinated the ruler, so, too, does Macbeth see the ghost of Banquo.  Yet, while Hamlet observes,

conscience doth make cowards of us all,/And thus the native hue of resolution/Is sicklied l'er with the pale cast of thought

Macbeth seeks to silence any tinge of conscience in anger and more murderous action--perhaps, to silence his conscience from making him a coward.  He shouts at the "spirit of Banquo, Down! (IV,i,112), and asks the "filthy hags" why they show him the apparitions, declaring,

I'll see no more,/And yet the eighth appears, who bears a glass/Which shows me many more.../For the blood-boltered Banquo smiles upon me, (IV,i,1118-123)

However, in Shakespeare's plays, ghosts often return to haunt a murderer, to act as his conscience.  That Macbeth may still possess some conscience seems plausible in light of his earlier remarks of Act II in his "Is this a dagger which I see before me" soliloquy.  In this speech, Macbeth reflects that

wicked dreams abuse/The curtained sleep;....and withered murder...Moves like a ghost. (II,i,50-56)

Then, after Macbeth commits the "deed," he tells Lady Macbeth that he has heard voices cry "Murder!" (II,ii,23), and that he believes that he has heard a voice cry

'Sleep no more!/Macbeth does murder sleep'--the innocent sleep (II,ii,34-35)

So, Macbeth's problems with sleep may, indeed, stem from tinges of conscience as they do for Lady Macbeth, who despite having "unsexed" herself in Act I and having orchestrated Duncan's murder becomes more human in her insanity, for this insanity has been brought on by her conscience.  Her madness is, indeed, guilt-ridden; and it deprives her of sleep:

Hell is murky...What, will these hands ne'er be clean?...Here's the smell of the blood still.  All the perfumes of Arabia will not sweeten this little hand....What's done cannot be undone. To bed, to bed, to bed! [she cannot sleep](V,i,36-71)