One of the factors to take into account when judging the small number of passages in Acts that are cited against justification through faith alone is how often only faith or repentance (two sides of the same coin) is mentioned as the means of receiving justification: 2:21, 3:16, 3:19, 4:4, 9:42, 10:43-44, 11:17, 11:21, 13:39, 13:48, 14:1, 14:27, 15:9, 16:31, 16:34, 17:34, 19:2, 26:20.
I'll expand on some of those passages, to clarify why I've cited them. Acts 3:16 refers to a healing, but it's probably the sort of double healing passage I've discussed elsewhere. The healed man is referred to as praising God after the healing and is described as following the apostles (3:8, 3:11). Both of those make more sense if he had converted than if he hadn't. And Peter and John don't say anything to the man about a need to do anything else in order to be reconciled to God, which also makes more sense if the man had already been reconciled to God. Furthermore, Peter refers to the healed man's faith as "the faith which comes through [Jesus]" (3:16). A reference to "the faith" makes more sense if it's a faith that people in general are supposed to have, not just people seeking a healing.
Some of the passages I've cited mention faith without mentioning justification (4:4, 9:42, 14:1, 17:34), but the passages make the most sense if faith is viewed as bringing about justification. If something more was needed for reconciliation to God, then it would make less sense to highlight faith so much and not mention more. Seeing these passages as referring to justification also aligns them better with the rest of the material in Acts, like the other passages cited above.
