You worry too much about things that your lawyer should handle. If you need to appear in Immigration Court, hire a lawyer and he/she will handle any potential admissibility issues. Judges have law clerks who prepare memos and the judge reviews the memos or the memo and the file before the hearing.
It looks like you are mixing up personal injury claims and criminal charges. If you are charged, hire a criminal lawyer to defend. If you he files a personal injury suit, hire a lawyer to defend the suit.
First, there is no INS. It is called USCIS now. Second, "the best way to legally do the marriage" - I am not sure I understand the question. Have the wedding of your dreams. Third, get married whenever you feel ready. Finally, if you were inspected upon entry and are otherwise eligible to adjust status, file -130, I-485, I-325, I131, I-765, I-864, I-693. You should hire an attorney if you are not familiar with the process.
Your post includes immigration and non-immigration questions. As long as you disclose the DUI, it should not be an issue for your citizenship application (provided you have no other brushes with the law). With respect to the fines, community service, license suspension, etc, you need to consult with a DUI/or criminal lawyer in Ca.