But Paul did not require every Gentile to be circumcised
There are reasons for Gentiles becoming circumcised that are in accordance with God's commands, so there are important lines being crossed between these three positions:
P1: Paul spoke against obeying God's commands for incorrect reasons, but never against obeying God's commands for the reasons for which they were given, so we should follow God's commands in the manner that Paul taught.
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P2: Paul spoke against obeying God's commands for the reason for which God commanded them and we must obey God rather than man.
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P3: Paul spoke against obeying God's commands for the reasons for which God commanded them as we should obey man rather than God.
--except that all were circumcised in heart.
Someone having a circumcised heart only refers to them being a doer of the Torah (Deuteronomy 30:6, Romans 2:25-29) while someone having a uncircumcised heart only refers to them not being a doer of the Torah (Jeremiah 9:25, Acts 7:51-53).
Act 15's list is not for mature believers. It is a tool for people in confusing times to figure out what to do.
I believe that some 'obedience to the Law' was perfunctory or to get into a circle for strategic reasons. One of those would be the vow or rite performed in Acts 21 to get access to the high priest where Paul needed to make a final warning to Israel.
How is that your "Paul" could not make a convincing enough case to save his neck at the end of Acts? Do you not take 'they worship night and day at the temple' in ch 26 to be their misguided practice, and not a compliment?
I don't have your answer about circumcision. It's not on the list for the beginning gentile believer. Why?
Even if you could answer all the questions the way you have, you have to come to terms, as I did, with the 'stoicheai tou kosmou' of Colossians and Galatians. The Law, in Gal 4:8-9, gets equated with the pagan practices of the initial stage of the Galatians:
1st, pagans
2nd, believers
3rd, imposed-upon-believers
4th, unburdened believers
The argument clearly is that there is no difference between where they started as pagans and where those 'under the Law' started.
When this expression is compared with 2 Peter 3's usage, it is clear that there is a type of pagan reverence for gaia that is the 'force' that causes its worshipper to maintain certain practices, and that Peter knew Judaizers who treated the Law the same way. This could not be disrupted.
In Colossians, this hollow philosophy that is discrediting believers (paralogizetai) is replete with neo-Judaistic features; angels have spoken; foods, seasons, days, moons are tangling the believers; the restrictions are ineffective; the 'humility' is a crass sham, etc, etc.
In regard to Colossians 2:8, the holy righteous, and good commandments of God are not taking people captive by philosophy and empty deceit, or according to human traditions, and Christ set a sinless example for us to follow of how to walk in obedience to them, so it doesn't work to interpret that warning that it is not according to Christ to follow his example. Paul fleshed out what he was referring as the elementary principles of the world in Colossians 2:16-23 as pagans who were promoting human traditions and precepts, self-made religion, asceticism, an severity to the body. Those promoting asceticism and severity to the body would be judging the Colossians for celebrating God's feasts, not for refraining from doing that.
If God saved the Israelites out of slavery in Egypt in order to put them under slavery to the Torah, then it would be for slavery for God sets us free, however, Galatians 5:1 says that it is for freedom that God sets us free. In Psalms 119:142, the Torah is truth, and in John 8:31-36, it is the transgression of the Torah that puts us into slavery while the truth sets us free. Moreover, the Torah did not come through the line of the slave woman, but came through the line of the free woman, so it is important to correctly identify what Paul was speaking against, and that should impact how Galatians 4 is interpreted.
Likewise, in Galatians 3:26-29, every aspect of someone being children of God, through faith, in Christ, and being children of Abraham and heirs of the promise is all directly connected with someone living in obedience to the Torah. Being a child of someone is metaphorically about embodying their likeness through being a doer of their character traits, which is why Jesus said in John 8:39 that if they were children of Abraham, then they would be doers of the same work as him. In Matthew 23:23, Christ said that faith is one of the weightier of the Torah, and in 1 John 2:6, those who are in Christ are obligated to walk in the same way that he walked. In Galatians 4:1-7, being under the elementary principles of the world is contrasted with the adoption as sons, receiving the Spirit, and being heirs through God. In Romans 8:4-14, Paul contrasted those who are born of the Spirit with those who have minds set on the flesh who are enemies of God who refuse to submit to the Torah, and in 1 John 3:4-10, those who are not doers of righteous works in obedience to the Torah are not children of God.
Galatians 4:8-9 Formerly, when you did not know God, you were enslaved to those that by nature are not gods. 9 But now that you have come to know God, or rather to be known by God, how can you turn back again to the weak and worthless elementary principles of the world, whose slaves you want to be once more?
In Exodus 33:13, Moses wanted God to be gracious to him by teaching him to walk in His way that He and Israel might know Him, and in Matthew 7:23, Jesus said that he would tell those who are workers of lawlessness to depart from him because he never knew them, so the goal of the Torah is to teach us how to know God and Jesus, which is His gift of eternal life (John 17:3). So those who formerly did know God does not refer to those who were formerly following God's instructions for how to know Him, but to those who were not formerly following the Torah, aka former pagans. Likewise, people who were enslaved to those that by nature are not gods is also clearly referring to former pagan who were not formerly following the Torah, so Paul could not have been criticizing them for returning to follow God's instructions for how to know Him. Rather, now that they have come to know God and by know by God in obedience to the Torah, they were returning to weak and worthless elementary principles of the world, so they were returning to following pagan holy days.
In 2 Peter 3:10-18, it says that Paul is difficult to understand, that those who are ignorant and unstable twist his words to their own destruction, to be careful not to be carried away by the error of lawless men, and to instead grow in grace and knowledge of our Lord and Savior Jesus Christ. In Psalms 119:29, he wanted God to be gracious to him by teaching him to obey the Torah, so the way to grow in grace and knowledge of our Lord and Savior Jesus Christ is by following his example of obedience to the Torah (Matthew 7:23). Moreover, we can be confident that when Paul is correctly understood that he did not promote the error of speaking against obeying the Torah.
I just read Titus 2. As usual I never get the sense that Paul is in the least concerned with regulations from the Torah. Prove me wrong.
How else do you think that the Israelites knew how to do what is godly, righteous, and good, and to renounce doing what is ungodly if not through the Torah?