You are correct that the NADA numbers are junk.
To my knowledge, the lowest priced 36ET to sell in the last couple of years sold for around $40,000. That particular boat had sunk, which will really knock the price down.
The highest price paid that I am familiar with was in excess of $170,000.
The boat you are looking at has been on the market forever. That raises all kinds of concerns in my mind. So get a good hull survey done, and a good engine survey done by a qualified Cummins tech. Be prepared to walk away.
Keep in mind, a 99 36ET that has been regularly maintained and is in very good overall condition will sell somewhere around $110,000 to $140,000.
1999 36 Express Trawler