One thing at a time.
The better translation and understanding of "through" in the above verse from which you have your understanding, is "in", meaning "in Christ." Which ultimately changes the meaning altogether...
Just another distinction without a difference.
to mean that it is not we who do the walking, but Christ, in whom we are made perfect, not in the flesh,
If you're still sinning in the flesh, then you're not walking with Jesus.
Separating our soul and spirit from our body is one thing, since we are souls temporarily in earthen vessels. But to separate our soul and spirit
from how we live in the flesh, is religious and spiritual hypocrisy.
Sinful works of the flesh only come from a lusting heart and filthy spirit.
Thou blind Pharisee, cleanse first that which is within the cup and platter, that the outside of them may be clean also.
Seeing ye have purified your souls in obeying the truth through the Spirit unto unfeigned love of the brethren, see that ye love one another with a pure heart fervently: Being born again, not of corruptible seed, but of incorruptible, by the word of God, which liveth and abideth for ever
Men can be outwardly righteous in appearance, with an unclean soul, but no man can be outwardly unrighteous with a clean soul. That's the fictitious stuff of 'faith alone' ideology. It's where people care more about what they think of themselves, than about what they are actually doing in life.
In the end, The Father will judge our works,
without any respect toward our beliefs and opinions about ourselves. All our personal little ideologies end in the grave.
He that saith he abideth in him ought himself also so to walk, even as he walked.
And the world passeth away, and the lust thereof: but he that doeth the will of God abideth for ever.
for it is not the flesh that is born [again] anew, but the spirit.
True. The flesh isn't redeemed until the resurrection of the just.
In the meantime, we are commanded to walk as Jesus walked in our own mortal flesh, even as He did in His.
I personally believe Christians ought to stop talking about all this superhero stuff with Jesus' body, as being different from men.
It's not just confusion but also a source of ready mockery, that Christians are teaching either pagan deified heroes, or Marvel Studio filmography.
'The Adamic Race' could make a good movie, I'm sure, but it's lousy Christian teaching.
Thus, none of this indicates that we become perfect and sinless in the flesh,
All this 'revelation' stuff just to say you're still a lusting sinner with the world?
Having therefore these promises, dearly beloved, let us cleanse ourselves from all filthiness of the flesh and spirit, perfecting holiness in the fear of God.
And the very God of peace sanctify you wholly; and I pray God your whole spirit and soul and body be preserved blameless unto the coming of our Lord Jesus Christ.
Wherefore, beloved, seeing that ye look for such things, be diligent that ye may be found of him in peace, without spot, and blameless.
Pure religion and undefiled before God and the Father is this, To visit the fatherless and widows in their affliction, and to keep himself unspotted from the world.
But as he which hath called you is holy, so be ye holy in all manner of conversation;
I believe the revelation of God in the Bible, especially pertaining to how we must walk and live through the faith and power of Jesus Christ.
but rather within the flesh we are made perfect and sinless in spirit.
I.e. lousy on the outside by really great on the inside.
Many people feel that way while getting drunk, but they know differently the morning after. I know this, because I used to be one.