Can anyone succintly describe the precise force of this particle?
succintly
= enclitic νυν (Willcock). see lsj II: 
http://www.perseus.tufts.edu/cgi-bin/ptext?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3D%2371309
Smyth can (#2928):
νύ > (enclitic; Epic and Cyprian), a still weaker form of > νῦν> , and less emphatic than > δή> . It is common in questions and appeals; less freqent in statements; as > τίς νυ> ; who now? Also after other particles, as > καί νύ κε, ἦ ῥά νυ> .