Showing that salvation, grace, delivery from the body of death, can not reached if one is weak: your own words support my view.
Rather than point out the weakness of your points, I'm going to tell you the plan of salvation as described by Scripture.
Then I will show where the points you support lead to, the plan of salvation you understand.
This is what happens:
The Christian life is described as a journey, a process.
How can a person be saved?
By believing on Christ, you and your family.
What does believing on Christ do? It takes you out of the influence of all that which is not of God and puts you under the influence of all that which is of God. When Israel left Egypt and was taken out of the influence of the world and was exposed to God. She drank from the Rock and the Rock was Christ. Yet with most of them God was not pleased and they wandered in the desert till they died, without entering rest.
If she was not under the influence of the world, but under the influence of God, would that not put a stamp on her as belonging to God?
We should not forget that it is not only our peers who influence us but also our own appetites. The drive to possess resources, relationships, power, sometimes even desiring the property, life partners the prestige belonging to others, covetousness. God wanted the Israelites to abandon all these appetites, even the desire for self preservation, and direct all their loyalty to Him, and He had given them enough reason to do so. However, only Joshua and Caleb acquired this spirit. Of all the adults that left Egypt, only these two entered the Promised Land. The children were later tested and they had the advantage of not growing up in Egypt and passed God's test of loyalty, a lesser test.
Becoming a Christian and going to church is the equivalent to drinking from the Rock. Children have a great advantage in growing up influenced by exposure to God's teachings and facing a lesser test, provided they are taught right.
Baptism is the recognition of the switch of loyalty from world and self to God. Apart from coming into contact with God's teaching, this repentance, change of outlook, mindset , also is accompanied, rewarded by the giving of the Holy Spirit. Are children given the Spirit? Clearly the Spirit is given only on belief, and children have no personal belief, following only in the footstep of the family. However the exposure to instruction and influence from God gives them a distinct advantage in deciding to be loyal to God: isolation from worldly influence, exposure to God's instruction, easier testing.
However it's important that teaching is coherent and comprehensive. Instruction that involves much incomplete conclusions, dogmatism, fideism, mystery and paradox will have an unfavorable influence on children and when they finally are able to have critical reasoning abilities, are able to think for themselves, they WILL notice those illogical and incomplete teachings that ignore the clear instructions in the Bible.
The text clearly lays out what is expected and what results, on right action.
Reflect, weigh the issues, choose to follow God. This is belief. Choosing and exhibiting loyalty to God. Leading to the sanctification of our spirits, which then places them with Christ in high places.
Now the same must be done with the body. Luther saw the Christian life as a series of confessions, so his theology was truly faith based. However, just as the baptismal confession resulted in salvation of our spirits, the agreement, con fess ion, aligning with God's opinion, that our bodies were in need of rejuvenation, leads to the sanctification of the body. This is where actions, good works, the transformation of the nature of our bodies, is required. That is why Luther valued the sacraments.
When observed, God responded.
Be baptised. God gives his Spirit. We are justified.
Confess. God gives His Spirit, we are sanctified.
This is how we start with faith and continue with faith, not by works.
Luther truly was against works of the law, something Wright, Dunn and Sanders fail to understand.
Putting to death the deeds of the body was confessing that we possessed a sinful body, and in confessing, agreeing with God about this fact, Christ is faithful and cleanses us of all unrighteousness. Walking in the light is the walking in the spotlight of God's holiness, which reveals those unrighteous habits.
If we refuse to confess, but cling on.to those desires of the flesh, justifying their place in.our lives, we will die. Our bodies will not be sanctified and enjoy the comprehensive resurrection, the better resurrection that Paul writes about. In fact, persistent returning to the flesh life leads to banishment from fellowship with God and His people, handing over to satan for the destruction of the flesh, so that even though the body may be destroyed, the spirit may be saved, but as through fire.
Does putting to death the deeds of the body through confession lead to full sanctification? Not really . Paul states that he pleaded with God to remove the remaining thorn on his flesh, but God wanted to remind him that it was grace that saved and that that grace was sufficient for full sanctification, acceptance.
So to summarise, agreement with God, loyalty, is what is needed, not a required amount of work, the total removal of all fleshly desires. Its the attitude, not the state.
THAT is why the verse says "make sure no one misses out on reaching grace“:
15See to it that no one comes short of the grace of God;
The Christian life is a journey. The writer knows it will take time to understand the teachings. He wants people to be nice to each other so that they can concentrate on drinking from the Rock. This way, they will be able to reach a condition where they have God's favour, grace. This is not perfection. Paul wanted perfection, but God said Paul was in His good books and that was sufficient!
This then is where the possibility of not reaching salvation is taught, with parallels found in many other places. In Galatians 3 the believers started out with faith and are now trying to reach grace by circumcision! This proves that your point is wrong, your insistence that faith brings about justification and sanctification in one step. It is clearly stated that it is a two stage process. In fact, Paul tells the people of they try to be circumcised they will fall out of grace, Christ, who ensured grace was now available, would be of no benefit for them. They would be like the old covenant believers who never had grace, whose only benefit was the guardianship of the law, the justification of the spirit, who did not receive rest, delivery from the body of death, the sanctification of the body.
Be careful of the minimalist teachings of the lazy scripture teachers. They take the revelation God gives them and do not expand on it, study it, go to Bible college maybe, but bury it in the ground and give it back to the master in its basic, original form, when they could at least have put it in the bank, asked for help from the Holy Spirit.
If a person follows your method, just believe Jesus is God, then he will be stuck at a halfway stage. He will not reach a stage where God's grace is on him, where God will say, "Before I never knew you fully acknowledged me, but now I know you do". This happened to Abraham after many years of walking with God, when he was transformed from a person who lied to save his life, to one who was ready to give up his most precious possession, his son Isaac.
