Is it permissible for a man who married in court according to the Hanafi madhhab to follow the fatwa that suspended and immediate divorces issued before the marriage contract do not take effect, and would his marriage be valid and not subject to divorce, or must he follow the Hanafi madhhab in all matters of divorce issued before the marriage contract?

The legally accountable individual is not obligated to follow a specific jurisprudential school of thought. Mentioning a particular madhhab during the marriage contract does not imply adherence to it in matters of divorce or other issues. Therefore, there is no objection for the questioner to marry in courts that adopt the Hanafi madhhab, while still taking the preponderant opinion that divorce does not occur before the marriage contract.