A car is only worth what someone is prepared to pay for. If he's willing to pay $35,500, then that's how much it's worth to him. If he offers more, then it's good for you and not good for him. I dont know how much your car is really worth if he didnt make you that offer, but if it's 100% original with low kms, no accidents, and is as good as you say, then it's worth more than your average R33 which are in the $20k's.
Some guy came up to me 2 months ago and said he was looking for a GT-R in exactly the same colour as mine. With only 185 being made in MP III, I told him yes it's not easy to find in that colour and you would have to import one yourself as mine was not for sale. But if someone offered me, say 20k above the price I paid for it, I would seriously consider selling to get a later model R34.