Russia has been making a lot of threats lately, including nuclear ones. That if NATO moves troops into the Baltics, then the Russians will, um, do something with their nuclear weapons. What? Is Russia willing to start a nuclear war if the US puts five or ten or twenty tanks into the Baltics?
If so, this basically means that Russia will use its nuclear threats anytime it wants to exert a veto on US/NATO policy. That, of course, is unacceptable. If placing US/NATO troops in the Baltics is something that Russia really does not want, then we should it unless Russia gives us something that we want, such as really respecting the deal with Ukraine....
However, that is unlikely and probably not enough. Russia has been playing salami tactics with us--taking small pieces, none big enough by itself to warrant much retaliation. The Baltics fear that they will be next. To deter that, the US/NATO should try some salami tactics of their own: send some small units to hang out in the Baltics, then reinforce a smidge and then declare that these units will be there for a while, and then later announce that the basing is permanent. At which point does Russia start nuclear over this?
If the threat is of fomenting dissent and trouble within the Russian speaking populations of the Baltics, there are political ways to handle this--lean on the governments of those countries to treat these people better, and engage in an information campaign (proproganda) to educate the Russian-speakers in the Baltics about how much fun it is to live in Crimea, eastern Ukraine or even Russia today.
I tend to make cautious recommendations, but my frustration here is the idea that only one side can take advantage of the stability-instability paradox. And I also don't want US foreign policy and NATO decisions to be subject to Russian nuclear blackmail. Nuclear weapons in this relationship should only be used for one's own security, and, indeed, they do, making the claims about Ukraine's importance for Russian security to be ... incredible.