In fact, only this, ...you forget, the seed of Abraham is not a racial issue, but a faith one, then you quote the passage in Romans that is talking about those who are "spiritual Israel," that is, the redeemed.
So you are applying verses entirely out of context to contradict the clear "in context" meaning of the verses you only partially quoted, namely:
Heb. 2:14-17 Forasmuch then as the children are partakers of flesh and blood, he also himself likewise took part of the same; that through death he might destroy him that had the power of death, that is, the devil; And deliver them who through fear of death were all their lifetime subject to bondage. For verily he took not on him the nature of angels; but he took on him the seed of Abraham. Wherefore in all things it behoved him to be made like unto his brethren, that he might be a merciful and faithful high priest in things pertaining to God, to make reconciliation for the sins of the people.
I do not know why you would try to make these verses say anything other than what they clearly say. "Forasmuch then as the children are partakers of flesh and blood, he also himself likewise took part of the same." Can there be any question of what the "same" refers to? Is it not flesh and blood, it referes to? But the writer goes on to say, "For verily he took not on him the nature of angels; but he took on him the seed of Abraham. Wherefore in all things it behoved him to be made like unto his brethren." How can this mean anything other than the fact his nature was perfectly human, inherited through His mother, the "seed of Abraham," that he might be like his brethern in "all things." Now, if he did not have the same kind of nature as is brethren, then He was not made like them in "all things."
As for the nonsense about Jesus being the seed of Abraham through "faith," does that mean Jesus was "born again" into family of Abraham like we are? And why would Jesus need to be born again?
I'm sorry if I have offended you. I believe you are sincere, and truly seeking the truth, but I fear that your heart has been moved from the simplicity that is in Christ. (2 Cor. 11:3) You do admit that you "system" is not exactly simple, and requires quite a bit of explanation, don't you? You have been doing a lot of explaining.
I think all systems which, "have all the answers," cannot be completely correct and contain some grave errors. If they did not, those who hold them would not condemn those who do not accept every nuance of their particular brand of Christianity, but declare with Paul, "...Let every man be fully persuaded in his own mind." (Rom. 14:5) I know this verse is talking about practice, but Peter reminds us Paul wrote some things that were hard to understand, 2 Pet. 3:16) so we must suppose every one didn't understand them, and that there were disagreements. Some things others demand we believe are things that have not been explicitly revealed at all, so no view may be rightly insisted on. (Deut. 29:29)
My purpose is not to convince you, and so long as our exchange was not offensive, it was interesting. I think I shall cease for now, to be sure I do not offend you.
God bless! Hank