Having therefore obtained (oun tuchōn). Second aorist active participle of old verb tugchanō.
The help that is from God (epikourias tēs apo tou theou). Old word from epikoureō, to aid, and that from epikouros, ally, assister. Only here in N.T. God is Paul’s ally. All of the plots of the Jews against Paul had failed so far.
I stand (hestēka). Second perfect of histēmi, to place, intransitive to stand. Picturesque word (Page) of Paul’s stability and fidelity (cf. Phi 4:1; Eph 6:13).
Both to small and great (mikrōi te kai megalōi). Dative singular (rather than instrumental, taking marturoumenos middle, not passive) and use of te kai links the two adjectives together in an inclusive way. These two adjectives in the singular (representative singular rather than plural) can apply to age (young and old) or to rank (Rev 11:18) as is specially suitable here with Festus and Agrippa present. In Act 8:10 (Heb 8:11) the phrase explains pantes (all).
Saying nothing but what (ouden ektos legōn hōn). “Saying nothing outside of those things which.” The ablative relative hōn is attracted into the case of the unexpressed antecedent toutōn and so ablative after ektos (adverbial preposition common in lxx, the papyri. In N.T. here and 1Co 6:18; 1Co 15:27; 2Co 12:2.). Cf. Luk 16:29 about Moses and the prophets.