1. Is a higher airframe with NDH necessarily bad?
Depends what the damage was, how well it was fixed, and how long ago it was (longer=better). If something was geared up 40 years ago, no problem. Somebody bent a wing last week? Problem.
2. What if the plane spent its entire life in a club?
Depends on the club. I'd buy a plane that spent its entire life my club in a heartbeat, because A) it's an equity club so the pilots are owners and care about the planes more, and [noparse]B)[/noparse] I know that we spare no expense on maintenance and every squawk is fixed as soon as it's reported. There are other clubs that can be pretty shady. Ask around and see what you can find out, but in general I wouldn't change much based on its being in a club. At least it was likely flown regularly for its entire life and that's why it's high time.
3. Is there a percentage increase in annuals for an older bird with higher hours?
Percentage? No. You'll likely have more squawks, and pay more to fix them, but how much more is always an unknown.
4. What about birds that have been flown 2x as much as average over its life?
Considering "Average" birds often spend months at a time in the hangar, more time can be better.
Take a look in the logbooks and note the TTAF at each annual. Given two airplanes, both 40 years old and with 8000 hours, I would MUCH prefer to buy the one that was flown 150-250 hours every year than the one that was flown 1000 hours a year for the first 7 years at a flight school, then was bought by someone who quickly couldn't afford to maintain it and sat in the hangar for 5 years, then was owned by someone for the next 28 years for 0-80 hours per year.
5. How do you discount a higher timed bird to come up with a fair price? Is VRef accurate (it seems high).
Depends why it's higher time. Look at the above and decide what it's worth to you, and what it's going to be worth to the next guy you try to sell it to. It'll be harder to find a buyer with a higher-time airframe or engine unless you have a competitive price.