Totally separate matters. The alimony would have stemmed from the civil divorce, the annulment is a matter of the Church's recognition of the marriage. Without the annulment, they were still married in the eyes of the Church, despite the civil divorce.
Yup, but I wonder if he tried to get himself off of paying alimony by claiming "hey, the Church said my marriage never
really happened..." (Probably not but I'll bet the thought crossed his mind)