Usually with the county or local office that issued the license, with copies or indexes at some state vital records offices.
In the case file at the court where the divorce was filed; some states also keep certificates or indexes at vital records offices.
Often in part, but financial details and information about children are frequently sealed or confidential under court rules.
No. They are claims made in a dispute unless the court made a specific finding, so treat them with care.
The license authorizes the marriage; the certificate or return records that the ceremony actually took place and when.