Fr. Reese, I think your insights here are helpful & show your openness to understanding the the Scriptures based on a critical, studious analysis, which I'm sure your theology study has taught you to do. I find this the most insightful way to read the Scriptures - in a studious, intellectually humble manner. 

And yet I wanted to add (& you may be aware of this argument) that the word that the translation that you provided renders as "unlawful marriage" may better be translated as "adultery". I understand that the Koine Greek word "porneia" is debated, but I read an intriguing argument for its being translated as "adultery" - in the sense of secretive sexual intercourse with a man other than the woman's husband - as the more accurate term. This is based on the fact that in the Septuagint translation, the word "porneia" is often used in a phrase alongside another Greek word, "moixeia", to translate OT Hebrew phrases in which both words, in each context, refer to such manner of adultery.