Can this Simoncini be saved?

That bubbling of the paint/rust around the bottom bracket area is the most ominous thing about the frame. It looks like rust that has eaten through from the inside.
Everything else is surface rust.
You could replace the scalloped downtube though, and it would probably be sound.
Depends what you want to pay for the renovation.

I'm not quite sure. As I said, those frame are nickeled (just like a new car), so any rust would be from the inside. Basically - rust with flaky paint to hold it together.