With regards to 2): the cultural history of Russia is pretty tangled and I don't think that Pan-Slavism is necessarily going to happen with democratization - Pan-Slavism does require a sense of 'belonging to a greater nation/race' which simply doesn't develop if you were an illiterate serf.
Even the idea of 'Russian-ness' amongst the peasantry was somewhat shaky up until Soviet times; an early mass democracy would have probably reinforced local tendencies.
In a cultural sense, mass democracy in 1900s Russia would pose a terrible dilemma for Pan-Slavism. The ideology based itself around the assumption that the Slavs had a better 'national character' for national/democratic development than the individualistic West - a deep spiritualism, concern for the greater whole, etc. I could imagine the Russian intelligentsia eagerly waiting for the serfs to elect noble, disciplined politicians to the Duma... only to have them return village elders, corrupt politicians and suchlike to St. Petersburg. It probably would have been a seminal point for Russian culture, the sort of realization that the serfs weren't actually as European as the intelligentsia assumed them to be. OTL this sort of stuff was probably behind works like the Rite of Spring.
However, I agree that Pan-Slavism would be a stronger factor were it a limited democracy - say, limited by income so only the middle classes and the rich could vote.