Hi Brian,
You have received some excellent advise from "professionals" who have experience actually doing survey work. Yes, walking away from a deal (I have done this) after spending a lot of money on the costs associated with surveying a boat is a bit painful, but that is nothing compared to the costs associated with owning a "bad" boat!!!!
As others have said, consider it money well spent either way (buy or walk) and learn something from the experience. I did.
My opinion, it is not fair to the seller to expect that he will pay for all or most of the repairs/replacements found during your surveys. It is an old boat after all and a lot of the items I mentioned in the other thread related to this survey are really maintenance items. Some will already be done, some will be part way to needing doing and some will need doing right away.
To me, as a buyer, you look over the boat carefully prior to an offer. You negotiated a price based on your estimate of the condition of the boat, and the market you are in.
After survey, you renegotiate based on large ticket items found wanting, or items that truly are at or near end of life. For example, I would expect a discount for a house battery bank that was 9 years old. It is done, or very, very close to it. If the bank was 6 golf cart batteries at $200 each, I would expect the seller to cover at least half that cost (so say $600). Now to me, it gets more complicated if the bank is say 4 years old. I would probably just accept that. Maybe not the best example as there are other factors, but you get the idea.
I talked about the raw water cooling system in my other post. As long as nothing major was found there (like neglect), I would service it myself and not expect the vendor to cover it at all. Difference to me is "maintenance" vs "repairs", at least to a point.
Also, be aware, that your insurer will probably "require" that you repair all items found by the survey within a fairly short time frame. Peter (Pau Hana) can comment more on that. If it is a long list of items (even if nothing expensive by itself) that can be used to renegotiate. Just don't be too unreasonable about renegotiating unless you are willing to not own the boat.
Good luck.