What is the best way to distinguish when God (the son) is talking in His human nature or in His divine? In Mark 13:32, Yeshua says:


  But of that day and that hour knoweth no man, no, not the angels which are in heaven, neither the Son, but the Father.


I'm going to use Ellicott's Commentary for English Readers since he is not as obvious as other commentators, and he says something interesting that I'll quote at the end: 


  Neither the Son.--The addition to St. Matthew's report is every way remarkable. It indicates the self-imposed limitation of the divine attributes which had belonged to our Lord as the eternal Son, and the acquiescence in a power and knowledge which, like that of the human nature which He assumed, were derived and therefore finite. Such a limitation is implied by St. Paul, when he says that our Lord "being in the form of God . . . made Himself of no reputation" (or better, emptied Himself), "and took upon Him the form of a servant." (See Note on Philippians 2:6-7.) It is clear that we cannot consistently take the word "knoweth" as having a different meaning in this clause from that which it bears in the others; and we must therefore reject all interpretations which explain away the force of the words as meaning only that the Son did not declare His knowledge of the time of the far-off event.


In Luke 22:42 Yeshua says:


  Saying, Father, if thou be willing, remove this cup from me: nevertheless not my will, but thine, be done.


Ellicott refers us to Matthew 26:39, in which he says:


  Now the "cup" is brought to His lips, and His human will at once shrinks from it and accepts it. The prayer which He had taught His disciples to use, "Lead us not into temptation," is now His prayer, but it is subordinated to that other prayer, which is higher even than it, "Thy will be done." In the prayer "If it be possible" we recognise, as in Mark 13:32, the natural, necessary limits of our Lord's humanity In one sense "with God all things are possible," but even the Divine Omnipotence works through self-imposed laws, in the spiritual as in the natural world, and there also ends cannot be obtained except through their appointed and therefore necessary means.


In John 20:17 Yeshua says:


  Jesus saith unto her, Touch me not; for I am not yet ascended to my Father: but go to my brethren, and say unto them, I ascend unto my Father, and your Father; and to my God, and your God.


Ellicott says:


  My God, and your God.--This phrase contains the same fulness of meaning, and adds the special thought of the continuity of the human nature of our Lord, which has already appeared in the word "brethren." 


So that seems simple enough. Anytime god the son says something that contradicts his divinity, we just ascribe this to his human nature. However, in John 14:28 Yeshua says:


  Ye have heard how I said unto you, I go away, and come again unto you. If ye loved me, ye would rejoice, because I said, I go unto the Father: for my Father is greater than I.


Ellicott says:


  On the part of those who assert the divine nature, it has been contended that the Father is greater than the Son only as regards the human nature of the Son; but this is not here thought of. In this passage, as in others of the New Testament, it is plainly asserted that in the divine nature there is a subordination of the Son to the Father.


So apparently ascribing one thing to his human nature while excluding his divinity is wrong, and probably some sort of Nestorianism.

What is the best way to distinguish when god the son is talking in his human nature or his divine?
Your question contains or suggests several good questions, but I will focus on the last paragraph. The historic Chalcedonian position on "What is the best way to distinguish when god the son is talking in his human nature or his divine?" is to not make such a distinction. 

For clarity, let me emphasise that in this answer I am assuming that God the Son specifically refers to the incarnate Word, Jesus Christ.

Historically, since the Third Ecumenical Council (Ephesus) most of Christianity has accepted that that distinction is not appropriate. This was expressed by the council in Cyril of Alexandria's fourth anathema against Nestorius:


  If anyone shall divide between two persons or subsistences those expressions (φωνάς) which are contained in the Evangelical and Apostolical writings, or which have been said concerning Christ by the Saints, or by himself, and shall apply some to him as to a man separate from the Word of God, and shall apply others to the only Word of God the Father, on the ground that they are fit to be applied to God:  let him be anathema.


The actions of Christ are to be attributed to the person of Christ  in which the two natures are united. We can say things like "Christ had the authority to forgive sins because the divine nature is united in His person." It is wrong, however, "The divine nature (to the exclusion of the human nature) of Christ forgave sins"

As to the Father's will, or how the Son is less than the Father, or how the Father is the God of the Son, those are other worthwhile questions.