It depends entirely on the type of person you are. If I were you, I would pick up Chem, and drop Physics. I love Chem and find it so interesting (despite the workload is quite heavy compared to physics), however Physics is sometimes draining (this depends entirely on the detailed studies you do, I have to do Structures and Materials instead of Special Relativity) and involves plugging numbers into a calculator, mindlessly. Chem involves understanding the topic properly (from every angle) and then the questions become easier. Physics, in my opinion, is a but trickier. But the decision is entirely your choice.
I would stick with Italian, not because of the scaling, but because its a break from all the maths/science subjects you have, and to enjoy it. There are a lot of advantages to taking a language in uni too, and overseas, like you said. I'm not sure of the pre-reqs of Physics tho, I know for in UoM there are heaps of courses involving Chem, but I think Physics is just an extra.
Or, on the flip side, you can always take Italian as your breadth at Uni, or learn it after school.
Coming from experience, I wish I stayed with learning French or Indonesian. It just adds that bit of diversity and variety, a breath of fresh air in a mindless drone of equations and numbers.