Hi Paull, can't comment on most of your questions (yet) but the wheels I suspect are to do with the polished finish - just like Themas, Dedras, Subarus and every other polished finish wheel, they look fabulous when new but unless you are anal about cleaning them, they will corrode quicker than a normal powder coat type finish. In saying that, all they need is a stone chip to break the lacquer or top finish and that is the start of it. Look great when new, rubbish for longevity. The wheels on the 2004 one I have just bought are 2 perfect, 2 starting to bubble - but they are a normal powder finish and the 2 can be refurbished at reasonable cost. Refurbishing diamond finish is trickier and will need a specialist.
I would say there can't be an issue driving one and putting the miles on, as you say there are lots with huge kms on them. The chap I bought mine from advised Alfa dealers here are the only ones who have the full Lanciiaa diagnostic kit, regardless of what Fiat dealers, and any specialists up north said. Once he found this out, his local Alfa dealer dealt with any issues - mostly electrics (what a surprise).
Lindsay