Was constrained by the word (suneicheto tōi logōi). This is undoubtedly the correct text and not tōi pneumati of the Textus Receptus, but suneicheto is in my opinion the direct middle imperfect indicative, not the imperfect passive as the translations have it (Robertson, Grammar, p. 808). Paul held himself together or completely to the preaching instead of just on Sabbaths in the synagogue (Act 18:4). The coming of Silas and Timothy with the gifts from Macedonia (1Th 3:6; 2Co 11:9; Phi 4:15) set Paul free from tent-making for a while so that he began to devote himself (inchoative imperfect) with fresh consecration to preaching. See the active in 2Co 5:14. He was now also assisted by Silas and Timothy (2Co 1:19).
Testifying to the Jews that Jesus was the Christ (diamarturomenos tois Ioudaiois einai ton Christon Iēsoun). Paul’s witness everywhere (Act 9:22; Act 17:3). This verb diamarturomenos occurs in Act 2:40 (which see) for Peter’s earnest witness. Perhaps daily now in the synagogue he spoke to the Jews who came. Einai is the infinitive in indirect discourse (assertion) with the accusative of general reference. By ton Christon Paul means “the Messiah.” His witness is to show to the Jews that Jesus of Nazareth is the Messiah.