Russia needs Crimea to secure it's excess to the Black see. Losing Crimea to NATO (or losing it at all) would be a huge problem. As long as you have Crimea - you basically control most of the Black Sea.
As for the Eastern Ukraine - best case scenario - securing a terrain pass to Crimea. Worst case scenario - destabilisation of the the country and more 'ground' during negotiations over any deal. Almost like taking hostages.
Military base is not stronghold anymore. You don't need to protect it from siege. Kaliningrad is just a place of location of strategic missiles of medium range. It single-use weapon. You don't need ground path to Kalinigrad.
As for the Eastern Ukraine - best case scenario - securing a terrain pass to Crimea. Worst case scenario - destabilisation of the the country and more 'ground' during negotiations over any deal. Almost like taking hostages.
Baltics don't have such values.