Your question is not clear to me, but I presume it like this.

You are interested in adding some quantity of lecithin in D/W totaling to 100 ml. How to express this concentration in %(w/v) and mMoles/kg?

Say, you have dissolved 758 mg of lecithin in D/W & made to 100ml volume.

%(w/v) = 758mg in 100ml = 0.758 g/ 100ml = 0.758%(w/v)

Mol. wt of lecithin = 758;    D/W - 100ml = 100g (by density)

758mg/100ml = (758mg/758) / 100g = 1mMole / 0.1 kg = 10 mMole/kg.

Generalizing for Lecithin in D/W:  1%(w/v) = 13.193 mMole/kg.