2A. The relationship between Romans 2:1-3:8 to what precedes it in Romans 1:18-32 is as follows: 1:18-32 is Paul’s description of the Gentiles dilemma and indictment with regard to their evil ways (i.e. lack of glorification and thanks to God, idolatry, sinful desires of the heart, shameful lusts, envy, arrogance, on and on…), while 2:1-3:8 is the confrontation by Paul of said things. A confrontational diatribe to whom? That is the question. Paul seemingly turns his discourse in 2:1 to the Jews, although I believe it is again his brilliant writing style under the clichéd heading of “two birds with one stone.” Keck states that “Paul does not implicitly turn to the situation of the Jew in 2:1 (as many still hold); rather, 2:1 clearly continues the indictment of Gentiles in 1:18-32.” Further, Keck goes on to say while that is clear, Paul also does it from a different perspective (hence, brilliant writing style). Both the Jews and Gentiles would have felt the ‘sting’ of the accusation (“you are without excuse”), regardless of whether the Greek second person singular “you” was being directed at a hypothetical interlocutor or one of them. However, here is the problem with the latter: God’s impartiality. Paul reasons that if God’s impartiality punishes evil deeds, then His impartiality also rewards good deeds as well, whether done by Jews or Gentiles. The baseline significance of God’s impartiality is further illustrated by its discussion between 1:18-32 and 2:1-3:8 – as Paul lists examples of sinful indictments, 1:25 would have specifically resonated with the Jews (cf. Jer 10:14), leading me to believe the list in and of itself was impartial – all were guilty; all would be culpable to God’s wrath. The usage and force of “therefore” in 2:1 further drives home the point. The description just given in preceding verses of the state of one group of the human race contains inherently the condemnation of the other, for it is equally applicable to both. By saying “You, therefore,” Paul guides the discussion toward the theme of accountability. Everyone is accountable; everyone has no excuse because “in passing judgment on someone else,” he is effectively condemning himself, since you (the judge) are doing the very same things.
2B. I believe the point in which Paul addresses a Jewish audience in Chapter 2 is at verse 17. I believe he reminds a Jewish audience beginning at verse 1 (although he was primarily addressing the Gentiles in 2:1-16). The significance of where Paul begins addressing the Jews is two-fold: one, he is reiterating accountability and alerts his listeners via the same means of “calling them out” just as he did in earlier verses with the Gentiles. By stating “if you call yourself a Jew” as opposed to “if you are a Jew,” Paul is perhaps suggesting that their self-image does not align with reality. He is attacking their hypocrisy, if you will. This direct address by Paul to them links back to the reminder in 2:1-16 that he knows they thought themselves a holy and privileged people by right and entitlement, all the while they were unthankful, rebellious, and unrighteous. Secondly, the significance of addressing a Jewish audience beginning in 2:17 is with regard to the law. Paul is letting them know that the Jew who is imperious with his knowledge of God (2:17-29) will be regarded as uncircumcised (2:26-27) and that this whole “impartial judging” is really, a matter of the heart (cf. Deut. 30:1-6). As Keck summarizes, there is no veritable distinction because while each people group reacts or misses the mark in a particular way that is different from the other, similarities within the original offense abound, i.e. “Both the Gentile ‘judge’ and the Jewish ‘teacher’ do what each rejects (cf. 2:1-2, 2:21-22); the Gentile thinks he can escape God’s judgment (2:3) and the Jew does not teach himself what he teaches others (2:21) because he assumes he does not need to.”
And I will just add for context: I wrote this hours ago.