This formula successfully accomplishes the result I sought in the question I posted above:
=ARRAYFORMULA(SUM(IF(LEN(O5:O200),--(REGEXMATCH(TO_TEXT(O5:O200),"(^|,|\s)\s*(" & TEXTJOIN("|",TRUE,ARRAYFORMULA(TEXT(ROW(INDIRECT("A"&DATE(2023,7,1)&":A"&TODAY())),"m/d/yyyy")))&")\s*($|,|\s)")),0)))