How was the test drive?
I'm not going to give you any advice re: pricing other than spend a few hours browsing the "Notable recent Sales" thread and you'll have more than your fill of data. Based on the few photos you shared, the car looks decent. I'd agree that you should be prepared to spend a lot of money sorting out "little" things.
When I bought my car back in '07, people on Rennlist (hadn't yet discovered Pelican) gave me the same advice - to have 15k at the ready, minimum. I didn't believe it, but I have spent multiples of that sorting, and improving (IMO) the car.
I'm not as freaked out by the 2 rust pictures as some of the folks on here seem to be, having spent my entire life living in the rust belt. Of course rust is never good, but that car doesn't look like it was driven on salted winter roads. Limited views in your photos, but thinks like the lower shock bolts into the trailing arms and the rear sway bar drop link bolts would be rusty as hell if that car spent any time on salty roads.
My '79 which spent its entire life prior to my purchase in the sunny southeast (primarily Atlanta area) had a rust spot in a similar spot on the b-pillar. It was
not rusting through from the inside of the fender well. Rain or car wash water seems to get trapped there, and under the quarter window. After 30 years, it can take a toll. I removed the quarter window, the underlying aluminium trim and found this:
the worst of it was under the aluminum trim, completely out of sight. Nothing on the underside of the fender, because that area can dry out properly.
Took everything down to bare metal, used rust converter, then primed, painted, clear coated it. Reinstalled the aluminum trim with "Dum Dum" (3m strip caulk), and finally resinstalled the window with new rubber.
Because I was concerned the same thing happened on the other side I pulled the window (needed new rubber anyway). As you can see, its fine.
Just a reference point for people to see that rust does not necessary indicate that a car was driven on salty roads. There are nooks and crannies on these cars that will trap rain and wash water and after decades it can lead to rust.