$30,000 is way too high. Hagerty values a 70 Nova with a concours resto at $24,000. 99% of people don't do concours. Excellent resto is valued at $19,400, and good at $14,900.
The guy sounds like he has his head in the clouds and is trying to get out of it what he has into it. That's not how it works with cars. I doubt even with common sense and proof that his asking price is too high he will want to budge on the price.