My opinion of the Alfa garage has gone down . . . .they wanted you to spend €1700 on a car that will,according to them,last twelve months???
They may be right about the pump,( I may be wrong but if the ecu thinks the engine isn't running,it will cut the fuel?)but as you say,for the price of a sensor,it's worth trying
I'd definitely get the opinion of your local mechanic,maybe he can read the codes,too?
Depending on how advanced the rust is,is it worth rubbing it down,treating it with kurust(or similar rust converter) then undersealing it? if done before the CT,it may give it another year or two?Just a thought
The creaking is almost certainly top wishbone bushes . . .think they are made of brie!
On the plus side,everything is better after a good lunch!