I'm really sorry to hear about all your hardships in managing to record that specific reading - my heart is with you and I'm happy it came out right eventually - heard it now and enjoyed it greatly!
The separation between light and darkness - between good and bad/ right and wrong is a fascinating idea:
We might ask ourselves why there is evil in the world? By myself - I don't think we can answer this - it's something inherent in god's idea that we can't understand.
but there are those claiming that bad was created in order for the good to be discernible - by contradicting it to the bad, we can understand and appreciate the good.
Just like we can understand light only when it's a separated entity from the darkness.
Thanks again @hebrew :)
Edit: And be well, I'll pray for your health in the ברכת כהנים tomorrow morning.