That is to be understood as to what faith alone means. By God's grace alone through faith alone in Christ alone.
If I said, after going to a well and getting a large bucket of water and transporting it to a village, "I brought this water with a bucket alone, and with a horse alone," I would be contradicting myself, right?
Only grace alone, when we get to the root of the matter, is how we are saved. This is true for both Old and New Testament Saints. The Old Testament Saints were saved after God's grace was bestowed in His revealing His will to men. This began with Adam and is seen in every believer mentioned in Scripture. Now, just as you mention "And we all wait the full redemption at His appearing," yet we are "saved" already, even so they were saved but awaiting "full Redemption." For them it was waiting for their sins to be covered by the Cross and the bestowal of eternal life through union with God and the redemption of the body and the Eternal State. For us it is the redemption of the body and the Eternal State. When the Rapture takes place the Church will receive their glorified bodies and will be that much closer to "full Redemption," whereas those living in the Millennial Kingdom will be born again and awaiting their glorified bodies (which can either take place at their deaths or at the end of that Age).
But everyone mentioned is "saved." But, not everyone mentioned is/was eternally redeemed. Meaning the Old Testament Saints, that is.
When Abraham was later (like some 50 years later) justified by his work, the LORD God who also justfied him was none other than the preincarnate Christ (Genesis 22:12; John 1:18; John 14:6) who appeared to him.
Please present Scripture to support a "pre-incarnate Christ." The term "Christ" is a title, whereas the Son of God is a Person. There was no Christ until the Son took up residence in the womb of Mary. This is why we call Messianic Prophecy...Messianic Prophecy. It foretells what is going to take place in the future. The Christ has a beginning in time, whereas the Son of God is Eternal God, the Creator. While I do take the view that it is the Son of God Who interacts with men in the Old Testament, He was not yet the Christ, and would not be until the Incarnation:
Hebrews 10 King James Version (KJV)
5 Wherefore when he cometh into the world, he saith, Sacrifice and offering thou wouldest not, but a body hast thou prepared me:
John 1 King James Version (KJV)
1 In the beginning was the Word, and the Word was with God, and the Word was God.
14 And the Word was made flesh, and dwelt among us, (and we beheld his glory, the glory as of the only begotten of the Father,) full of grace and truth.
John 18:37
Pilate therefore said unto him, Art thou a king then? Jesus answered, Thou sayest that I am a king. To this end was I born, and for this cause came I into the world, that I should bear witness unto the truth. Every one that is of the truth heareth my voice.
Isaiah the prophet wrote of it as if it were a past event, Isaiah 53:1-12.
Again, this is why it is called Prophecy. Much of Revelation is spoken of in a past tense, yet we do not think that has been fulfilled, or that it was fulfilled at the time of the writing (some hold to the view that it is not a literal description of future events).
And Abraham with all the OT saints were taken to be with Christ at His ascension (Ephsians 4:8).
We agree that the Old Testament Saints did not go to Heaven when they died, the question is...why not?
Because they awaited Redemption through Christ, their sins had not yet been atoned for on an eternal basis, merely in a temporal context through the provision they had...animal sacrifice.
If you back up you will see that the Writer makes it clear that it was not until Christ died that the sins of the Old Testament Saints were redeemed:
Hebrews 9:12-15 King James Version (KJV)
12 Neither by the blood of goats and calves, but by his own blood he entered in once into the holy place, having obtained eternal redemption for us.
13 For if the blood of bulls and of goats, and the ashes of an heifer sprinkling the unclean, sanctifieth to the purifying of the flesh:
14 How much more shall the blood of Christ, who through the eternal Spirit offered himself without spot to God, purge your conscience from dead works to serve the living God?
15 And for this cause he is the mediator of the new testament, that by means of death, for the redemption of the transgressions that were under the first testament, they which are called might receive the promise of eternal inheritance.
The "blood (death) of bulls, goats, and heifers" was the provision the Old Testament Saints had, and those sacrifices did not bring about remission of sins or atonement on an eternal basis, only the Blood (Death) of Christ can do that. We see marked in time His death and institution of the New Covenant. The Old Testament Saints were in need of redemption from the (Covenant of) Law, even the ones prior to the Covenant of Law being established, because "the Law" can also have a general application to the revealed will of God in any Age. When the Law was established it did not vary from the revelaed will men had been given before that, so those who were guilty of breaking the Law in the Ages prior to the Age of Law had to be redeemed as well.
Note that we also see that the promise of eternal inheritance is made sure by His death as well.
Hebrews 9:22-24 King James Version (KJV)
22 And almost all things are by the law purged with blood; and without shedding of blood is no remission.
23 It was therefore necessary that the patterns of things in the heavens should be purified with these; but the heavenly things themselves with better sacrifices than these.
24 For Christ is not entered into the holy places made with hands, which are the figures of the true; but into heaven itself, now to appear in the presence of God for us:
Again we see the distinction between His death and the death of animals. And that was the only provision they had. There is nothing in Scripture that applies the Atonement and Reconciliation on an eternal basis to the Old Testament Saints, and much that teaches the exact opposite.
In regards to v.28:
Hebrews 9:28 King James Version (KJV)
28 So Christ was once offered to bear the sins of many; and unto them that look for him shall he appear the second time without sin unto salvation.
I would agree that this speaks of the redemption of the Body, primarily for those raptured, and secondly for those who go through the Tribulation.
God bless.