That's a very nice example from 2 Maccabees. Quite compelling in its parallel, especially tying an action "on behalf of the dead" to the resurrection.
As for the adverb, this is what White says: "The adverb hOLWS is then understood to function attributively in its clause, modifying NEKROI rather than EGEIRONTAI, precisely in order to distinguish it from and set it against the metaphorical usage immediately preceding it; hence in translation, 'truly dead persons' " (p. 493). In the footnote he refers to the attributive usage in BDF, par. 434, and he also says: "Here we agree with both O'Neill ("1 Cor 15:29," 310) and Murphy-O'Connor ("Baptized," 540), who gives a cogent argument in favor of this rendering. The adverb hOLWS occurs sparely in both biblical and extrabiblical literature. Of the five biblical occurrences, three are found in 1 Corinthains (5:1; 6:7; 15:29; the other two are found in Matt 5:34, and a variant LXX reading of Job 34:8). In all three instances, the connotation 'actually' or 'truly' seems likely...In 1 Cor 6:7, the context suggests that Paul uses hOLWS to denote by means of contrast what he views as a true defeat (hoLWS HTTHMA), namely, the very fact that the Corinthians are suing each other in courts of law, as opposed to that which the Corinthians construe as defeat, namely, that they are being wronged and defrauded. According to our rendering in 1 Cor 15:29, then, Paul's usage of hOLWS is uniform throughout 1 Corinthians, not only semantically but also syntactically, coming immediately before the word it modifies. For an extrabiblical example of hOLWS with the unequivocal sense of 'actually' or 'truly,' see P. Oxy 1676.29-31: KALWS OUN POIESEIS EL[QOUS]A TW MESORH PROS [EMAS] hINA hOLWS IDWMEN SE."
Not that I necessarily agree with his analysis, just to put his argument out there for due consideration....