Jacob was considered the firstborn, but he wasn't really the first born - Essau was. If you do a lexical study on the word firstborn / only begotten in most of these contexts you quoted - it is referring to the one that is dearest and the one with God;s blessing. Essau did not get the blessing but sold it. Ishmael was first born, but the blessing of the firstborn rested on Isaac. I also believe that is the way the term was and is used for Jesus. Lets look at what is written in Isaiah 53 which clearly lines up with everything about Jesus: Who hath believed our report and to whom is the arm of the Lord revealed...
Who has believed our message
and to whom has the arm of the LORD been revealed?
2 He grew up before him like a tender shoot,
and like a root out of dry ground.
He had no beauty or majesty to attract us to him,
nothing in his appearance that we should desire him.
3 He was despised and rejected by men,
a man of sorrows, and familiar with suffering.
Like one from whom men hide their faces
he was despised, and we esteemed him not.
4 Surely he took up our infirmities
and carried our sorrows,
yet we considered him stricken by God,
smitten by him, and afflicted.
5 But he was pierced for our transgressions,
he was crushed for our iniquities;
the punishment that brought us peace was upon him,
and by his wounds we are healed.
6 We all, like sheep, have gone astray,
each of us has turned to his own way;
and the LORD has laid on him
the iniquity of us all.
7 He was oppressed and afflicted,
yet he did not open his mouth;
he was led like a lamb to the slaughter,
and as a sheep before her shearers is silent,
so he did not open his mouth.
8 By oppression [a] and judgment he was taken away.
And who can speak of his descendants?
For he was cut off from the land of the living;
for the transgression of my people he was stricken.
9 He was assigned a grave with the wicked,
and with the rich in his death,
though he had done no violence,
nor was any deceit in his mouth.
10 Yet it was the LORD's will to crush him and cause him to suffer,
and though the LORD makes [c] his life a guilt offering,
he will see his offspring and prolong his days,
and the will of the LORD will prosper in his hand.
11 After the suffering of his soul,
he will see the light of life [d] and be satisfied [e] ;
by his knowledge [f] my righteous servant will justify many,
and he will bear their iniquities.
12 Therefore I will give him a portion among the great, [g]
and he will divide the spoils with the strong, [h]
because he poured out his life unto death,
and was numbered with the transgressors.
For he bore the sin of many,
and made intercession for the transgressors.
