Well thought out post, thank you.
But I do wonder about this comment of yours:
"1. People have questioned why the fiancé didn't report her missing."Let's say she had texted to tell him that she was breaking up with him, that she was having a mental breakdown and needed some space, that she had intent to self-harm, that she was running away to pursue some adventure/passion/ex/lover, that she was using some sort of controlled substance and didn't feel safe with the baby, that she was checking into rehab/recovery etc...
Even if any of the above ^^^ was said, why wouldn't he call LE to report her missing? If she said she was having a breakdown, or was feeling suicidal, wouldn't that be an important reason to call LE and call her friends and family, to try and find her quickly?