You can easily find low sodium food across Italy since mediterranean cuisine has many ingredients containing minimum amount of sodium (fish, vegetables, fruit, etc).
Be careful at the way they are cooked and you should avoid completely famous pasta dishes such as carbonara or cacio e pepe.
Majority of restaurants welcome special requests and you can specify your needs when ordering. Better learning some basic words in Italian (devo mangiare cibo senza sodio, senza sale, no parmigiano...and so on).
Of course decaf coffee is available in Italy! All bar/cafe' have it and many restaurants too.
It can be difficult to find it in cheap places such as osterie and trattorie but typically bars remain open until late and you can easily get it also after dinner.