The borders are pro-Russian and that's a major issue? Maybe. But if they take Ivangorod and Pechory, all they're doing is adding more territory populated almost exclusively by Russians. I thought Narva was bad enough, you know?
Yes, based on my readings from the 1918-1927 time period. The were universally consider pro-Russian borders by the Baltic people. And if one wants pro-Russian people, they can't feel cheated. And your exclusively Russian statement is just false at least as far as the areas near the border. In most of them, they would not have be majority anything. The question would be what is the Plurality. And a lot of these areas had low overall population. And we are not talking massive border movements, probably under 50 miles. The Balts were not calling for annexation of all or even most of what has become Belarus. The Russians simply chose some extra land over long-term good relations with the baltics. Taking land over good relations is hardly unique in history. IMO the Russians made a mistake. A lot of the land once you get away from the coast is low value northern timber. And the Balts would have been useful allies, since at this time the Russians are too weak to win decisively against the Poles.
Of course Lithuania keeping its 1920s borders is just asking for trouble on a long-term scale, especially without Stalinist population exchanges.
But frankly, I don't see how good relations could be had no matter what Russia did, given how it was once an occupying power. The nationalist movements in all three immediately took xenophobic and right-wing forms and the idea that these are ethnic democracies has not died to this day.
On the population exchanges, they can't really be avoided when one starts forming nation states where the majority plurality is often under 40%, and which race is majority varies from one town to the next. You have limited choices - Build nation states and use ethnic cleansing, have an empire like Austria or Russia where one ethnic group dominates, or find the Swiss model with a lot of autonomy. Unfortunately, the Swiss model is not really viable in Russia or A-H after WW2 due to the attitudes of the people and leaders.
While some/many may disagree, in the fallout of WW1, you will get ethnic cleansing by the winners and often the losers. When looking at it from my TL and looking at the writings of the day, there is basically no one calling for tolerance. Not the Poles, Germans, Russians, Balts, etc. Basically the only group not calling for ethnic states with the best rights going to the majority ethnic groups is the Jews, and the Jews probably understood that a Jewish state was not in the cards.