I don't think Paul would have referred to them as pagans, because they did not subscribe to one of the cults of the area. And such people would not have been in a synagogue; they were in the agora. The god-fearing would have been non-jewish who respected what they heard in synagogues...
"Nevertheless, what saith the Scripture?" Gal. 4:30A.
Earlier, Paul had preached at Pisidian Antioch (in Galatia)...
Acts 13:38 Be it known unto you therefore, men and brethren, that through this man is preached unto you the forgiveness of sins: 13:39 And by him all that believe are justified from all things, from which ye could not be justified by the law of Moses.
In other words, the Law had concluded "the whole world under sin" (both Jew and Gentile) but Christ died for our sins, Rom. 3.
Galatians 2:14 But when I saw that they walked not uprightly according to the truth of the gospel, I said unto Peter before them all, If thou, being a Jew, livest after the manner of Gentiles, and not as do the Jews, why compellest thou the Gentiles to live as do the Jews? 2:15 We who are Jews by nature, and not sinners of the Gentiles, 2:16 Knowing that a man is not justified by the works of the law, but by the faith of Jesus Christ, even we have believed in Jesus Christ, that we might be justified by the faith of Christ, and not by the works of the law: for by the works of the law shall no flesh be justified. 2:17 But if, while we seek to be justified by Christ, we ourselves also are found sinners, is therefore Christ the minister of sin? God forbid. 2:18 For if I build again the things which I destroyed, I make myself a transgressor. 2:19 For I through the law am dead to the law, that I might live unto God. 2:20 I am crucified with Christ: nevertheless I live; yet not I, but Christ liveth in me: and the life which I now live in the flesh I live by the faith of the Son of God, who loved me, and gave himself for me. 2:21 I do not frustrate the grace of God: for if righteousness come by the law, then Christ is dead in vain.
That is also the actual context of the following...
Acts 17:1 Now when they had passed through Amphipolis and Apollonia, they came to Thessalonica, where was a synagogue of the Jews: 17:2 And Paul, as his manner was, went in unto them, and three sabbath days reasoned with them out of the scriptures, 17:3 Opening and alleging, that Christ must needs have suffered, and risen again from the dead; and that this Jesus, whom I preach unto you, is Christ. 17:4 And some of them believed, and consorted with Paul and Silas; and of the devout Greeks a great multitude, and of the chief women not a few.
Reminding them later, of the actual spiritual state he had found them in, when he first met them (because worship via the Law was now idolatry, 2 Cor. 3; Heb 10), Paul wrote the following about them...
1 Thessalonians 1:8 For from you sounded out the word of the Lord not only in Macedonia and Achaia, but also in every place your faith to God-ward is spread abroad; so that we need not to speak any thing. 1:9 For they themselves shew of us what manner of entering in we had unto you, and how ye turned to God from idols to serve the living and true God; 1:10 And to wait for his Son from heaven, whom he raised from the dead, even Jesus, which delivered us from the wrath to come.
So, no, neither those religious Jews, nor those God-fearing Gentiles were in the right anymore.
Both were now no better off, this side of the Cross, then the Pagan worshipping Gentile.
Both were now considered "sinners of the Gentiles" or heathen...
Galatians 1:15 But when it pleased God, who separated me from my mother's womb, and called me by his grace, 1:16 To reveal his Son in me, that I might preach him among the heathen; immediately I conferred not with flesh and blood: 1:17 Neither went I up to Jerusalem to them which were apostles before me; but I went into Arabia, and returned again unto Damascus.
Romans 11:30 For as ye in times past have not believed God, yet have now obtained mercy through their unbelief: 11:31 Even so have these also now not believed, that through your mercy they also may obtain mercy. 11:32 For God hath concluded them all in unbelief, that he might have mercy upon all.
Might as well have quoted Ephesians 2, by the way. It is the exact same thought.
Acts 17: 11, 12.