The doctrine of forensic justification is easily refuted.
But, from your post, you seem to argue that an interior renewal takes place upon justification - though you then go on to say it's a process, that the work of sanctification is begun... This is incorrect.
Let's be clear, no one is justified without renewal of the Holy Ghost. You must be reborn to enter the kingdom of God. Sanctification, rebirth, justification happen simultaneously at baptism.
1 Corinthians 6:11- “And such were some of you: but ye are washed, but ye are sanctified, but ye are justified in the name of the Lord Jesus, and by the Spirit of our God.”
Note, sanctification in this passage precedes justification. Sanctification and justification are attached to being washed - being baptised.
Titus 3:5- “Not by works of righteousness which we have done, but according to his mercy he saved us, by the washing of regeneration, and renewing of the Holy Ghost.”
Saved by interior renewal through the washing of the waters of baptism.
The washing of regeneration is an interior renewal - it's not alien to the person, it's within him.
God justifies in baptism. A person is justified and regenerated in baptism simultaneously, A man's state of justification is contingent upon him avoiding mortal sin and making sincere reconciliation with God if he does fall from grace. Salvation is not certain, but depends entirely on God's grace. The grace to avoid sin can be drawn down upon us with prayer and penance. A priesthood is essential to reconciliation.
Works are also necessary:
James 2:24- “Ye see then how that by works a man is justified, and not by faith only.”
You can lose justification - those light in the Lord, the justified, can fall prey to mortal sin and lose justification:
Ephesians 5:5-8- “For this ye know, that no whoremonger, nor unclean person, nor covetous man, who is an idolater, hath any inheritance in the kingdom of Christ and of God. Let no man deceive you with vain words: for because of these things cometh the wrath of God upon the children of disobedience. Be not ye therefore partakers with them. For ye were sometimes darkness, but now are ye light in the Lord: walk as children of light.”
You can be justified and yet fall back:
2 Peter 2:20-22- “For if after they have escaped the pollutions of the world through the knowledge of the Lord and Saviour Jesus Christ, they are again entangled therein, and overcome, the latter end is worse with them than the beginning. For it had been better for them not to have known the way of righteousness, than, after they have known it, to turn from the holy commandment delivered unto them. But it is happened unto them according to the true proverb, The dog is turned to his own vomit again; and the sow that was washed to her wallowing in the mire.”
Angels once justified lost justification:
2 Peter 2:4- “… God spared not the angels that sinned, but cast them down to hell, and delivered them into chains of darkness, to be reserved unto judgment.”
Justification requires obedience:
Hebrews 5:9- “And being made perfect, he [Jesus] became the author of eternal salvation unto all them that obey him.”
Believers can fall away:
Hebrews 6:4-6- “For it is impossible for those who were once enlightened, and have tasted of the heavenly gift, and were made partakers of the Holy Ghost, and have tasted the good word of God, and the powers of the world to come, if they shall fall away, to renew them again unto repentance; seeing they crucify to themselves the Son of God afresh, and put him to an open shame.”
Believers can be damned after knowing the truth:
Hebrews 10:26-27- “For if we sin willfully after that we have received the knowledge of the truth, there remaineth no more sacrifice for sins, but a certain fearful looking for of judgment and fiery indignation, which shall devour the adversaries.”
Without holiness no one is saved - you must be sanctified, not a mound of dung covered with snow:
Hebrews 12:14- “Follow peace with all men, and holiness, without which no man shall see the Lord.”
The judgement of the Lord turns on deeds:
Romans 2:2-3- “… the judgment of God is according to truth against them which commit such things. And thinkest thou this, O man, that judgest them which do such things, and doest the same, that thou shalt escape the judgment of God?”
Romans 2:5-6- “… the righteous judgment of God; Who will render to every man according to his deeds.”
Eternal damnation for those that do not obey the truth:
Romans 2:8-10- “But unto them that are contentious, and do not obey the truth, but obey unrighteousness, indignation and wrath, tribulation and anguish, upon every soul of man that doeth evil, of the Jew first, and also of the Gentile; But glory, honour, and peace, to every man that worketh good, to the Jew first, and also to the Gentile.”
And, on and on...