Eh, I'll give this a quick shot.
1-2: Italy remains divided, and the principal of Romantic Nationalism gets doused in a flood of cold water. Rather, pan-Nationalism takes on a more conservative character as it becomes increasingly defined as a top-down directive from strong states through careful planning as Bismark becomes the trailblazer in the movement.
3: Yes, and as a result get the impression that "Intervention works". This could lead to earlier co-operation in putting the kibosh on Prussia, triggering an earlier war that's a combination of the Franco-Prussian and Brother's War with Prussia and the North German Confederation aligning against a Franco-Austrian alliance over some issue of influence in the minor German states. Likely Piedmont uses the distraction to take another crack at the powers propping up the conservative regimes in the penninsula by invading while the Great Powers are distracted, with the end result either being the governments of those states band together and kick Victor's armies into next Tuesday, or they defect in hopes of getting privlages within a new alliance/nation and we end up with an Italy only a decade or so late, with a more decenteralized structure resembling something more like the USA or the German Empire
4. Yes, due to the economics of it all.