Is the described marriage contract valid given the doubts about the witnesses and the presence of the bride's father? And do certain statements and actions, such as threatening the wife with divorce, using allusive terms, swearing an oath of divorce during sleep, or saying "leave me," constitute a divorce? What is the ruling on Salat al-Istikhara performed with the intention of ending the marriage if a divorce occurs?

Since the judge married you according to the Madhhab (definition) of Abu Hanifa, your marriage is valid. The presence of one man with the judge during the عقد (marriage contract) is sufficient for witness, as long as both of them are Muslims. As for the divorce mentioned in the question, it does not take effect, because it is either a promise, a narration, or doubts and whispers. None of these result in divorce. Furthermore, Istikharah (seeking guidance from Allah) does not result in divorce, and it is not prescribed for such a matter; rather, it is prescribed when embarking on a permissible matter. The summary is to completely and thoroughly disregard whispers.