Acts 18:5 (Inceptive Use?)

I am drawing my Acts 18 discussions to a close; after this post, I will conclude with vss. 24-28, which narrate details about Apollos, a devout Jew from Alexandria. But this entry will concentrate on Acts 18:5 now.

Greek (WH): Ὡς δὲ κατῆλθον ἀπὸ τῆς Μακεδονίας ὅ τε Σίλας καὶ ὁ Τιμόθεος, συνείχετο τῷ λόγῳ ὁ Παῦλος, διαμαρτυρόμενος τοῖς Ἰουδαίοις εἶναι τὸν χριστὸν Ἰησοῦν.

Translation (NASB): "But when Silas and Timothy came down from Macedonia, Paul began devoting himself completely to the word, testifying to the Jews that Jesus was the Christ."

Issues: How should we understand the verb συνείχετο (from συνέχω), which NASB renders "began devoting himself"? J.B. Phillips translates the entire verse thus: "By the time Silas and Timothy arrived from Macedonia Paul was completely absorbed in preaching the message, showing the Jews as clearly as he could that Jesus is Christ."

Darrell Bock (Acts, BENTC): offers this explanation: "The verb συνείχετο (syneicheto) is imperfect and has an ingressive force (became 'absorbed in' or 'devoted to'). The verb can have the meaning of being 'constrained' or 'compelled' to do something (BDAG 971 §§6–7). The dative τῷ λόγῳ (tō logō) has the syntactical force of reference or respect: Paul devoted himself 'with respect to' the word (Moulton and Turner 1963: 220)."

NET Bible appeals to BDAG and likewise translates the verb inceptively: "Paul became wholly absorbed with proclaiming the word"

NWT 2013: "When, now, both Silas and Timothy came down from Mac·e·doʹni·a, Paul began to be intensely occupied with the word, witnessing to the Jews to prove that Jesus is the Christ."

F.F. Bruce: "he was able therefore to concentrate on the preaching of the gospel, and he sought to convince his Jewish hearers that the promised Messiah had come, and had come in the person of Jesus."

See The Book of Acts (New International Commentary on the New Testament) (Kindle Locations 12149-12151). Eerdmans Publishing Co - A. Kindle Edition.

The verb διαμαρτυρόμενος refers to the witnessing, preaching or testifying that Paul did in Corinth: it is a present middle participle. See Deuteronomy 30:19; Acts 20:21; 28:23; 2 Timothy 2:14; 4:1.

Just who were these Jews? In view of previous conversations here, I wonder if we can limit these individuals to Judeans.