Please read this again.
Genesis 15:6 And he believed in the LORD; and he counted it to him for righteousness.
Paul explains this further in
Romans 4:
Romans 4:1 What shall we say then that Abraham our father, as pertaining to the flesh, hath found?
2 For if Abraham were justified by works, he hath whereof to glory; but not before God.
3 For what saith the scripture? Abraham believed God, and it was counted unto him for righteousness.
4 Now to him that worketh is the reward not reckoned of grace, but of debt.
5 But to him that worketh not, but believeth on him that justifieth the ungodly, his faith is counted for righteousness.
That last part you posted is a part of neither Scripture.
Romans 4;5 is surely against works, as is Titus 3:
Titus 3:3 For we ourselves also were sometimes foolish, disobedient, deceived, serving divers lusts and pleasures, living in malice and envy, hateful, and hating one another.
4 But after that the kindness and love of God our Saviour toward man appeared,
5 Not by works of righteousness which we have done, but according to his mercy he saved us, by the washing of regeneration, and renewing of the Holy Ghost;
6 Which he shed on us abundantly through Jesus Christ our Saviour;
7 That being justified by his grace, we should be made heirs according to the hope of eternal life.
Here is the ABRAHAMIC COVENANT in its context. You should notice that the promise preceded the fulfillment of any sort of obedience. the context of this is where God changed the first name of Abram to Abraham, meaning "Father of many".
Genesis 15:1 After these things the word of the LORD came unto Abram in a vision, saying, Fear not, Abram: I am thy shield, and thy exceeding great reward.
2 And Abram said, Lord GOD, what wilt thou give me, seeing I go childless, and the steward of my house is this Eliezer of Damascus?
3 And Abram said, Behold, to me thou hast given no seed: and, lo, one born in my house is mine heir.
4 And, behold, the word of the LORD came unto him, saying, This shall not be thine heir; but he that shall come forth out of thine own bowels shall be thine heir.
5 And he brought him forth abroad, and said, Look now toward heaven, and tell the stars, if thou be able to number them: and he said unto him, So shall thy seed be.
6 And he believed in the LORD; and he counted it to him for righteousness.
7 And he said unto him, I am the LORD that brought thee out of Ur of the Chaldees, to give thee this land to inherit it.
8 And he said, Lord GOD, whereby shall I know that I shall inherit it?
9 And he said unto him, Take me an heifer of three years old, and a she goat of three years old, and a ram of three years old, and a turtledove, and a young pigeon.
13 And he said unto Abram, Know of a surety that thy seed shall be a stranger in a land that is not theirs, and shall serve them; and they shall afflict them four hundred years;
14 And also that nation, whom they shall serve, will I judge: and afterward shall they come out with great substance.
15 And thou shalt go to thy fathers in peace; thou shalt be buried in a good old age.
16 But in the fourth generation they shall come hither again: for the iniquity of the Amorites is not yet full.
17 And it came to pass, that, when the sun went down, and it was dark, behold a smoking furnace, and a burning lamp that passed between those pieces.
18 In the same day the LORD made a covenant with Abram, saying, Unto thy seed have I given this land, from the river of Egypt unto the great river, the river Euphrates:
19 The Kenites, and the Kenizzites, and the Kadmonites,
20 And the Hittites, and the Perizzites, and the Rephaims,
21 And the Amorites, and the Canaanites, and the Girgashites, and the Jebusites.
Ultimately, what I do not see is Scriptural support for the position that obedience precedes the promise. That would make the promises of God conditional, and is totally in opposition to the Great Theme in Scripture that grace precedes any promise.
What you seem to be promoting is actually a Mormon doctrine. I am NOT calling you that, but here for your reference is the source for my statement:
2 Nephi 15:23 For we labor diligently to write, to persuade our children, and also our brethren, to believe in Christ, and to be reconciled to God; for we know that it is by grace that
we are saved, after all we can do.
Since this is really an Evangelical forum, I will not discuss Mormonism further except to state the obvious that nothing in the BoM, excepting the things copied from the KJV can be found in the Bible, and their jesus is so different that any one attempting to make the case that the Mormon jesus is the same Jesus Christ as if found in the Scripture ALONE is clearly attempting an impossible and irrational task.