My take on these pix...
The rust stains on the bow pulpit flange: I'd pull the pulpit. I suspect you will find minor corrosion
on the underside of the flange (no big deal) and/or corrosion
of the fasteners. Also possible leakage into deck core
if it is present in that area. Clean up flange, replace fasteners and re-bed. If there is core moisture, that is a different problem, and more difficult to address. Many descriptions of the process here on CF.
mildew: Something that happens, especially when aboat is closed up for a while. Due to condensation
on the headliner, and almost certainly a cosmetic-only worry.
Skeg crack: That's a worry indeed. Have you tried a vigorous shaking back and forth of the rudder
, whilst carefully watching the crack? Generally beyond internet
judgement, but worthy of careful investigation in the yard.
Chainplate: I'd expect to find some possibly severe corrosion of the plate and of the fasteners there. Replacement of the s/s strap would likely be in order, but really not so big a deal if the picture shows the whole thing. As to the condition of other chain plates, they are most likely of quite different construction than the one in the middle of the foredeck. If a good visual inspection
does not show similar rust issues I see no reason to condemn them out of hand. Of course, it is always better to pull and inspect if possible, but that may be beyond the purview of a prepurchase survey.
Usual caveat about "I ain't no expert, but"...
Good luck with your decision.