Converting a selection to Black & White

SCENARIO 1:  Somehow in the application of adjustment layers, the text inside the red rectangle below turned from black to green.  So I lassoed the area and clicked on the letters with the Color Range tool, then applied a Black & White adjustment layer and brought all the sliders down as low as they could go.  This resulted in text that was a very dark green, not true black (screen shot 2).  Obviously I don't understand how this adjutsment layer works. 

SCENARIO 2:  To the left of that area is more text which I turned black by selecting it and applying a Color Fill Layer and choosing #000000.  That worked, but the black was too dark for my taste.  So I applied a Curves layer to lighten the shadows somewhat but this resulted in exposing green (see screen shot 3).  How can I lighten the shadows here (text letters in the area to the left of the red rectangle) without exposing the original green again?  Thanks.