It took about 2 years, but Austria capitulated. In the one massive battle, I had 100K+ troops against 200K Austrians, and Austria (and Ottos) tossed over 600K more men into the meat grinder, while I added about another 150K, which meant that it dragged on close to forever. I had a +3 Defensive general at the start, and was punting posterior, but then he died and the next general in line was a +0, so the kill/casualty ratio dropped to only about 3:2, not 2:1 or better as in most of the other battles. I didn't want to break off, because the Austrian side was low on Organization, and I had hopes of them breaking (with nowhere to retreat to), but it didn't happen. Eventually, I sent troops to bypass the province completely, and managed to besiege Vienna. Eventually, Vienna and about a dozen other provinces capitulated before the 1-1/2 year battle was over, and Austria surrendered while it was still unresolved. Nasty, expensive, and senseless violence. I need to avoid that kind of situation in the future. At least it tied up the better part of a million Austrian troops while I took the provinces.
Pulling Sardinia-Piedmont out of France's sphere and allying them was one of the best moves leading up to the war, since S-P did an admirable job of fending off all of the various Italian states in Austria's sphere, as well as several Austrian stacks of 20-30K each. I had to provide some support by sending two stacks of 30K men to the northern part of the country to deal with some Austrian units, but S-P handled the rest admirably. The Bavarian army, in comparison, crumbled almost without a fight, and I had to drive the Austrians out of there almost by myself to prevent their early surrender. The Ottoman units coming up to support Austria just about melted away on contact, and were not much of a factor in the war.
I guess the next step is to repair the somewhat battered army and try to pry a couple of France's allies and spherelings away over the next year or so, before fighting France over A-L. The high dissent in the newly annexed Bohemian region (gotten without a point of Infamy) means that I can't rely too heavily on units recruited from there for a while, but at least it's a few hundred thousand men that Austria won't have if they try to take it back, and nicely developed and heavily German-populated prime real estate (with a lot of coal). Unfortunately, France just allied with the UK while I was fighting Austria, so taking on France, Russia, and the UK, plus several smaller countries in France's sphere simultaneously, doesn't sound promising. I think I need to promote Soldiers and recruit at least another 100K men or so.
In theory, I have a navy, but I've put almost nothing into it in favor of land combat. After 1860 or 1870, once I research and invent Monitors, that will change, and there will be a crash building program; no point in building a massive fleet of obsolete ships in the mean time.