You aren't really short. More average. Maybe short in Swedish terms but fairly average in Italian.
No idea what your frame is like. Different people carry weight in different methods. What sizes do you wear? In other words how big is your chest and waist.
If you're buying shirts S/M/L then you'll get whatever the company sticks you with.
Dress shirts are sized by collar size. Do you know your collar size? Then start looking for brands with a body similar to yours.
Company being? Shop? Factory?Most shops aren't setup for international VAT free sales. If they don't collect they risk having to pay it themselves.Manufacturers are more likely to have an in house process.Usually when you buy something on vacation you then file for a refund.