So many questions ---
That's the gist of where he's left at this point by the survey and just the general situations. Questions to which the answers could be widely variable. If the boat had been sitting as long as it appears without use, it probably shouldn't have even been run without being checked further and some things addressed. At any rate he doesn't know whether the engines are running hot or not, can achieve WOT or not, are in reasonably good shape or not. Same with the generator. He was left with more questions than answers.
Now, has the OP fallen in love with this specific boat and is he determined now to buy it regardless? I don't know. I know we're not talking about a $50k boat, but a $500k boat which I would hold to different standards, although the purchaser of the $500k boat might be better prepared to deal with unexpected costs.
He still needs an engine survey in spite of what he's saying about the greatness of the surveyor. At least he hasn't relayed to us what one would expect from an engine survey.
Also, he mentions surveyor's verbal comment. Is he working off verbal or the written survey?
At this point it's all a big gamble. It's either back up and get some things fixed and a good engine survey after those items required to have one are fixed, pretty much back to square one or it's make an offer based on worse case, buy boat as is, and take it to a good boatyard. If $500k is a fair price in good condition (I don't know if it is or not), then with all the unknowns, if I was going to gamble it would probably be at $400k, but then I'm not a gambler. A true gambler might go $450k. I personally don't like the unknown.