What is Macbeth's state of mind in Act 1 Scene 7? I know that his state of mind is disoriented and he is debating whether to kill Duncan. What...

Macbeth is quite concerned about the repercussions of killing Duncan.  He says,

If it were done when ’tis done, then ’twere well

It were done quickly. If the assassination

Could trammel up the consequence, and catch

With his surcease success; that but this blow

Might be the be-all and the end-all here,

But here, upon this bank and shoal of time,
We’d jump the life to come. But in these cases
We still have judgment here [...] (1.7.1-8)

He fears that the whole business of Duncan's murder won't be finished when he commits the murder.  If the one act could catch up and prevent any consequences, then the murder would be the end of things, and he would gladly do it.  However, as it is, there will be consequences (punishments) in this life.

The Divine Right of Kings meant that the king was God's chosen ruler; he was to be the head of his kingdom because God made it so.  Therefore, the injunction against killing a king was thought to be a religious imperative.  However, if Macbeth kills a king, he will inadvertently teach others that they could kill him, after he's become king, as well.  He says that, in committing the murder,  

[...] we but teach
Bloody instructions, which, being taught, return
To plague th' inventor: this even-handed justice
Commends the ingredients of our poisoned chalice
To our own lips. (1.7.8-12)

In other words, he will teach others that one can kill the king, and those "instructions" might come back to hurt him.  In essence, he could eventually be the recipient of his own violence. 

Macbeth feels incredibly torn because, emotional and conflicted, because there are so many reasons not to kill Duncan: he's Macbeth's kinsman, king, his guest.  On top of this, Duncan is a virtuous and excellent king.  In the face of all these compelling reasons not to murder Duncan, Macbeth can think of only one reason to move forward.  He says,

I have no spur
To prick the sides of my intent, but only
Vaulting ambition, which o'erleaps itself
And falls on th' other. (1.7.25-28)

Therefore, only his ambition spurs him on.  However, rendering him even more conflicted, he realizes that ambition often leads people to behave rashly and make mistakes.  He is doubtful and concerned, a little scared of himself and what he's planning, certainly worried about the consequences, and also doubting whether or not it is even the best thing to do.