Being stonewalled at the courthouse, how do I get them to take me seriously?

Have you contacted the local genealogical or historical society to ask them what they know about the situation? Also, there are message boards/forums on a variety of genealogical websites for every county in the country. You might try posting your dilemna there and see if anyone from the county might know something or perhaps be able to tell you who to call. Another resource might be the local library. I tried for 5 yrs. to get the date of death and obit for a relative and had given up. But one day, I decided to look to see if his little town in rural Iowa had a library. Sure enough they did and I called there and the lady put me on hold and went and found his date of death. She then took my email address and said she'd find the obit in their little local paper and send it to me. That was such a pleasant surprise because there was absolutely nothing about his death at the courthouse. So perhaps another approach might help dig up the info you need. Good luck.