I think I get Rom. 3:1-8. God has a global problem (see Genesis 1-11); God elects Israel to solve that problem but Israel falls victim to the same problem (see Genesis 12ff). So now God has two problems. But God’s faithfulness means not being satisfied with punishing the guilty, but rescuing both Israel and the world.
I don’t get Rom. 2:25-29, puzzled by at least three things. First, if Paul’s argument holds, there are by definition no disobedient Jews. Second, it’s not clear that Paul’s argument helps Paul, for he still agonizes over his fellow Jews who don’t acknowledge Jesus (chapters 9-11). Third, the stark contrast between keeping and breaking the law (v.27) is hard to square with our experience of the wide spectrum of unfaithfulness-faithfulness among both Jews and Christians. Help!