On (a). In this discussion I will substitute "Second International Strategy" for "Social Democracy" and "Third International Strategy" for "communism." My belief is that _both_ are historical relics.
On the second I approach it with two assumptions: (1) that the metaphor of "punctuated equilibrium" best catches the history (and future) of political change and (2) that in periods of political change the priority of act to theory is core. This is _not_ a rejection or even a modification of Lenin's view of the crucial role of theory, a view that remains fundamental. But if you read WITBD carefully, and with some awareness of Russian political history in the 1890s, it becomes clear that Lenin's emphasis on revolutionary theory _presupposed_ an upsurge of "spontaneous" political activity on the part of the working class. What Lenin recognized was that such "spontaneous" political activity would fail unless it was raised to the level of theory! That part of "Leninism" has survived the collapse of Third International politics because it is a simple description of reality and not merely a prescription for a particular species of political organizing.
As I have frequently argued over the last 6 years on this list, the timing and the nature of the "punctuations" in the political equilibrium are quite unpredictable. This does not represent a politics of mere quietism or "attentisme," however, but rather calls for constant efforts by leftists of various tendencies to push various forms of resistance to capital. Whether the current struggles around Bring the Troops Home Now! will develop into such a punctuation remains to be seen, but currently it's the best game in town as it were.
But Social Democracy is surely as dead as a road to the future as is Third-International Communism.
Carrol