Did a divorce occur with the husband's statement to his wife: "If you do not return now, then you are divorced," given the context of the husband's anger and his desire for her to return home, and with the wife's knowledge that she was menstruating at the time of the dispute?

What you uttered is considered a conditional divorce, contingent upon your wife not returning home immediately. Since she did not return as you mentioned, the divorce has taken effect. Her being in menstruation does not prevent its occurrence, as divorcing a menstruating woman is valid according to most scholars. If this divorce is the first or second, you may take her back as long as she is still within her waiting period (iddah). One should be cautious about using divorce pronouncements for intimidation.