Now the survival of Austria-Hungary always struck me as interesting because it was on the cusp of the mass urbanization stage of a demographic transition. The cities are going to absolutely explode in population as people from the countryside move to them. Within a generation or two the Empire is going to be more more urban than rural with a majority of the population living in the cities. This creates an interesting situation and IMO it it naive to assume Austria would inevitably fall apart. You will have a dozen ethnic groups living together. What will they be doing? What language would they use to speak to each other? The "core" of the Empire would shift from the various "nations" that it was composed of and instead move to the cities and the infrastructure connecting them. This situation strikes me as being survivable enough for Austria to last to the modern day.
The linguistic situation in the Habsburg lands would probably bifurcate between local languages for rural areas, and each nationality's provincial capital (assuming Magyar dominance ends and there is a Danubian federation of sorts), and a German speaking elite in cities like Vienna, Prague, Pressburg/Bratislava, Lemberg and Budapest. Two versions of German would develop in the same way that there is a native English dialect in parts of the EU like the UK and Ireland, but there is also an EU English spoken by L2 or L3 speakers in Brussels as a language of union-wide business and politics.
Jewish languages would vary widely across the Empire. In Austria and Bohemia most Jews lived in urban areas and became assimilated German-speakers, and there was a sizable migration of Ostjuden from Galicia and Bukovina that may have eventually assimilated to German as well. In 1908, the first international conference on Yiddish was held in Czernowitz, Bukovina (now Chernivtsi, Ukraine). Yiddish was likely to become the major language of Jews in Galicia and Bukovina, and Yiddish could gain a new lease on life if there are also Bundist institutions to support it throughout Eastern Europe.
Pressburg/Bratislava seems like a good compromise location for a national institution's headquarters, its centrally located but not associated with one language like Vienna or Budapest. Austria-Hungary could end up distributing its branches of government among multiple capitals like South Africa, and complement a Viennese lower house of parliament with a a central Bank and/or judiciary in Pressburg and an upper house of provinces in Budapest.
The Habsburg lands could also end up with a version of the West Lothian question where autonomous status is gradually granted to each non-German speaking group, but the German-speakers of Austria and the Sudetenland lack a distinctive province or parliamentary representation of their own aside from the Imperial Parliament in Vienna.
Russia is in dire, dire, dire, need of land reform. It can sustain a humongous population but not with the economy it had or was on track of having. I doubt Nicolas II would be able to stomach such a reform though. It would be to radical for his Tsarist mentality despite how necessary it needs to be. So despite how much farmland Russia had, IMO it was due for another revolution. There is a reason the whole time period from 1905 to 1917 is lumped together by historians. The reforms needed for the survival of the regime were too radical for it so the regime is going to get the boot. No more Absolute Monarchy of the Tsars. Even if Russia avoids the famine and revolution though it isn't roses for them anyway.
Various people on this site have said in the past that Russia was heading into a middle-income trap and I happen to agree with them. The problem with MITs is that once your stuck in one it can take decades to get unstuck. I can imagine that TTL economists would have an entire wing to studying the Russian economy and the rights and wrongs of it. Even so, a capitalist Russia would still be a tremendous improvement over the Soviet Union and would have one of the largest economies in the world, it just can't match per capita consumption of the likes of Germany, the UK, or the USA.
All the industrial gains of the OTL USSR and more could have been accomplished without the steep human costs of Stalinism. A moderate (compared to the Bolsheviks) SR government that enacts land reform, a parliament with actual power, legal equality for Jews, and some kind of autonomy for nationalities is the most likely result of a revolution against the Czar.
Russia wouldn't necessarily end up in a middle income trap. Even if the SRs are committed to democracy, there's a chance they could hamper industrialization the way the Congress Party-ruled India stagnated under the License Raj. Russia could end up going through a long period of failed socialist development, followed by free market reforms between the '60s and '80s, or a move towards a more dirigiste system like Japan's MITI or post-WW2 France with state support for "national champions", export subsidies, joint venture requirements for foreign investors, and some tariffs or import quotas.