Not as though I had already attained

GC
Your position is biblically untenable.

Oh it sounds real religious, modest and humble, but will in fact, send you to hell.
You are pinning your hopes on an inherent righteousness that is infuuuuused into you, but that righteousness comes and goes like the waves of the sea and will remain IMPERFECT until the day you die, as Paul admitted (Phil 3:9-12).

That is correct. It is precisely as St. Paul describes:
Philippians 3:9 And be found in him, not having mine own righteousness, which is of the law, but that which is through the faith of Christ, the righteousness which is of God by faith:

10 That I may know him, and the power of his resurrection, and the fellowship of his sufferings, being made conformable unto his death;

11 If by any means I might attain unto the resurrection of the dead.

12 Not as though I had already attained, either were already perfect: but I follow after, if that I may apprehend that for which also I am apprehended of Christ Jesus.

Alert: An imperfect righteousness will NOT get you to heaven.

That is true. That is why, those who are imperfect will have to go to Purgatory. Or, are you saying that St. Paul is not in heaven?

The truth is, that we are constituted as righteous by the "OBEDIENCE OF THE ONE" says the Romans 5.

There is more to it than that:
Hebrews 5:9
King James Version (KJV)
9 And being made perfect, he became the author of eternal salvation unto all them that obey him;

As it says, just as by the offense of one (Adam) came upon all men, condemnation; likewise by the righteousness of one, will justification come to all that believe.

Believing presumes obedience. 
Philippians 2:12
King James Version (KJV)
12 Wherefore, my beloved, as ye have always obeyed, not as in my presence only, but now much more in my absence, work out your own salvation with fear and trembling.

If you believe, you will obey also. In other words, it requires faith and works. Faith is believing. 
Romans 16:26But now is made manifest, and by the scriptures of the prophets, according to the commandment of the everlasting God, made known to all nations for the obedience of faith:

The entire life and death of Christ is subsumed into one ACT of righteousness, per 5:18, and this act of righteousness cannot be madethe act of many, EXCEPT BY IMPUTATION.

You need to look at all of Scripture. Not just one here and one there. The gift spoken of is the gift of the Holy Spirit:
Acts 2:38
Then Peter said unto them, Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins, and ye shall receive the gift of the Holy Ghost.

It is because of Christ's sacrifice that we can now be infused by the grace of the Holy Spirit, poured out upon us in Baptism:
Acts 22:16

King James Version (KJV)
16 And now why tarriest thou? arise, and be baptized, and wash away thy sins, calling on the name of the Lord.

The conclusion is that you are trusting in the sanctifying work of the Holy Spirit IN you to merit your salvation,

That is correct. Our salvation is God's work:
Philippians 2:11-13
King James Version (KJV)
11 And that every tongue should confess that Jesus Christ is Lord, to the glory of God the Father.


12 Wherefore, my beloved, as ye have always obeyed, not as in my presence only, but now much more in my absence, work out your own salvation with fear and trembling.


13 For it is God which worketh in you both to will and to do of his good pleasure.

which the Bible denies---

Where? Produce chapter and verse.

and refuse to trust in what Jesus did FOR you,

That is what Jesus did for us. By His Sacrifice, He established the Sacraments which are the washing of the Holy Spirit in His Body and Blood.

which results in the righteousness of Christ imputed to you,

Infused. The imputation or crediting of righteousness goes hand in hand with the infusion of righteousness. 

The Sacraments are pre-judgment events. When we come before God, believing His promises, He imputes it to us as righteousness. In other words, when we believe what God promised and come before Him for the Sacraments, He credits to us as righteousness. Then, He infuses us with His grace, effectively washing us of sins.

whole and entire and able to stand before the Judgement Seat on that final day.

At least you understand that we will all stand before the Judgment Seat on the final day. Most Protestants deny that fact.

However, judgment comes to the Church FIRST, through the Sacraments of God's grace:
1 Peter 4:17

King James Version (KJV)
17 For the time is come that judgment must begin at the house of God: and if it first begin at us, what shall the end be of them that obey not the gospel of God?

P.S. Don't bother trying to say that the R.O.C. infuuuused is enough to make you stand in confidence on Judgement Day because your theology doesn't bear that out.

We stand in hope:
1 Thessalonians 5:8But let us, who are of the day, be sober, putting on the breastplate of faith and love; and for an helmet, the hope of salvation.

You know the sanctifying work of the Spirit remains INCOMPLETE, otherwise were it sufficient, you would have no need for purgatory!

That is correct. Only those who have been perfected in this life will go directly to heaven. Those who remain imperfect must go t purgatory. God judges who fits which category.

Not you.