My answer/view to your opening question (Do we hacve fallen sin natures or not now?) --- in brief is that like a battery having two poles (positive and negative) fallen mankind has a fallen bipolar nature of good and evil where the good pole and the evil pole are both pulling on our wills.
The following is a re-post of a post I put on another thread, but that thread was closed before any comments could be made about my post contents.
I believe that fallen mankind is capable of making free will choices to accept or reject the gospel message. I believe in the inherent free will ability of fallen unsaved mankind to accept/believe or reject God’s call/drawing/convicting/convincing/persuading teaching work using the creation, the Word of God, and the Holy Spirit (Rom. 1:18-20; Rom. 10:8-17; 1Thess. 2:13; Heb. 4:12; Luke 8:21; Jn. 15:26, 16:13; 2 Thess. 2:13).
If just having knowledge of good and evil means/indicates that man is fallen and condemned, then why is not God’s nature also fallen and condemned because Gen. 3:22 states that man (Adam and Eve) has become like God knowing good and evil? However, the majority of Scripture indicates that God’s nature is pure good (holy, righteous and just); therefore, it is probably not just possession of mere knowledge of good and evil that indicates that Adam and Eve (mankind) are condemned and fallen since God already told Adam and Eve what was the good thing to do (to obey His commands) and what the evil thing to do (to disobey His commands) was before they sinned by disobeying God’s instructions; therefore, because of Romans 2:15 and 7:23, I believe most likely it is an internal fallen corrupted bipolar nature of good and evil (one pole is good and the other pole is evil), not a single poled fallen nature of evil, produced in Adam and Eve (as Cavinists and Arminians teach) when they sinned by disobeying God’s command that condemns fallen mankind, and this fallen bipolar nature of good and evil is what internally drives mankind to do good and evil (at the discretion of their free wills) and also gives mankind an inherent internal knowledge of good and evil. Calvinist’s teach that fallen mankind has only an inherent single poled nature of evil that does not move/drive men and women to do good. This fallen bipolar nature (having a good pole and an evil pole) in fallen mankind would account for the inherent internal drive to do both good and evil and also give mankind inherent internal basic knowledge of good and evil after many generations later when mankind had lost all verbal and written records of information from God following the fall of man in the garden of Eden. Many Calvinists teach that a person has to be indwelt first by the (Holy Spirit) (regenerated, born again) in order to obtain a will to do the good thing of believing in Christ as their savior. All Calvinists teach that man has to have God first perform an effective magical supernatural transformation of a person’s will into a believing will (even if they do not call it regeneration, born again) because they believe man’s internal single poled evil nature does not have a good pole that also internally drives man to do good, especially the good of making a free will decision to repent and accept Jesus as their savior.
In the book of Romans, God through Paul gives strong evidence that mankind has a bipolar nature having two poles (one pole is good and the other pole is evil). In Rom. 2:15 the Holy Spirit states through the Apostle Paul that the gentiles have the law written in their hearts which I believe, is strong, biblical evidence of the good spiritual pole of the bipolar nature of fallen mankind. In Rom. 7:23 the Holy Spirit has the Apostle Paul state that a law of sin dwells in his members which I believe, is strong, biblical evidence of the evil spiritual pole of the bipolar nature of fallen mankind. I believe this spiritual bipolar fallen nature of good and evil pulling on the will of man also gives man what the Bible calls a conscience, Rom. 2:15.
Therefore, I believe it is more accurate to described fallen mankind as being born corrupted bipolar sinners [The unsaved old man (Rom. 6:6; Eph.4:22; Col. 3:9)] having bipolar hearts/natures (“the heart is deceitful above all things….” – Jer. 17:9) with two spiritual poles (good and evil) because of Adam’s and Eve’s sin; that is, fallen/corrupted/sinful mankind has a spiritually bipolar nature of good and evil, a good pole and an evil pole (Gen. 2:16-17; Gen. 3:1-7; Rom. 1:19, Rom. 2:14-15, Rom. 7:15-25) internally pulling on our free wills, rather than just externally pulling on our wills as took place with God’s external commands and instructions and the external temptation of the serpent that took place in the garden of Eden – thus, man knowing and doing good and evil is the result of the fallen bipolar nature received when Adam and Eve sinned by eating of the tree of the knowledge of good and evil. Because one pole of man’s bipolar fallen nature is evil, it inclines unsaved mankind and saved mankind towards sin and good, thus ensuring that morally capable people will sin and not be able to live a perfect sinless life. The new man (born again person) is a Christian born again (indwelt by the Holy Spirit and should be willingly walking in/after the Spirit); that is, the new man has a good spiritual pole, an evil spiritual pole and the indwelling Holy Spirit all pulling on our wills and we should be (of his/our own free will) willingly walking in/after the Spirit (Eph. 3:16, Eph. 4:24; Col. 3:10; 2 Cor. 5:17; Rom. 7:24-8:26; Gal. 5:16-25) in order to have higher success rate of more consistently living Godly lives.
I refer to myself as an “inherent-free-willer” Christian, which means I believe in the inherent free will ability of fallen unsaved mankind to accept/believe or reject God’s call/drawing/convicting/convincing/persuading teaching work using the creation, the Word of God, and the Holy Spirit (Rom. 1:18-20; Rom. 10:8-17; 1Thess. 2:13; Heb. 4:12; Luke 8:21; Jn. 15:26, 16:13; 2 Thess. 2:13).
My limited knowledge of early Christian history, so far, has led me to conclude that when the early Christians concluded that fallen mankind had only one single poled nature of evil, the door was opened for pagan unconditional determinism and unconditional predestination to be easily injected into Christianity (by saying man lost his free will capacity to choose good or evil when Adam and Eve disobeyed God's command to not eat of the tree of the knowledge of good and evil) ultimately resulting in the development of an anemic puppeteering, bipolar good and evil nature of God concept and Calvinism's no free will of man TULIP soteriology.