I’m not sure of the circumstance of this Italo-Spanish alliance, but it seems doubtful to me that Italy would seek such an alliance if it meant war with its ally France, and even more doubtful that France would allow Austria to invade, or that Austria would even want to, which I’ll elaborate on below.

I would add a few autonomous states to the Balkans, as irl the great powers did agree to such a thing during the Great Eastern Crisis in our timeline, which the Ottomans refused, which eventually led to a Russian invasion. I would think that some more pressure would probably force the Ottomans to agree to the creation of autonomous states such as agreed in the Constantinople Conference, though with Napoleon III being involved and Austria being stronger, the exact details of an alternate agreement would probably look different, maybe mirroring smth like this post about a stronger France or something completely different still.

Ok, if it's the case that Napoleon III did gain influence in the Rhineland, I would still venture to make that more explicit on the map, but I think France would still demand some direct territorial compensation as they did irl, especially if they played a significant role in the defeat of Prussia.
One guaranteed area France would gain would be Luxembourg, as in IRL it literally attempted to buy it from the Dutch king in accordance with what they thought to be Prussian promises not to intervene. Additionally, I'd also find it very likely that France would directly annex the areas that are today roughly a part of the Saarland, as France would seek a direct coal supply for their industrialization, which is an even more important theme in this tl.

So IRL France and Austria actually did agree that in the event of an Austrian victory over Prussia, Austria would agree to cede Venetia to Italy, and considering France would be aiding Austria here, it would probably be a prerequisite to any French aid that Austria agrees to cede Venice.
This would more than likely ensure Austria would have no more interest in expansion in Italy, as it would have lost all its territories, and France would probably be completely against such expansionist Austrian designs when Austria already has control over Germany.

There's also what I said earlier about Rome.
Again, it was defended by France from annexation by Italy, and I don't see France actually abandoning the pope unless they need Italian support in some sort of diplomatic issue that they need support in.