If he does not retake ACT, where is he likely to land?
If he does not retake ACT, what is he doing instead with his time?
If there is time to prep with a specific goal, that could be worthwhile. Ten -fifteen hours test prep with tutor could raise his score one point. My D20 raised her 31 to a 32 with 33 superscore last June - July.
Are there merit awards at his safeties that become within reach with higher score?
Or will his time be better spent on other elements in his applications?