Hey, Pinz, he was funding his cheating sessions with cash from the sale of her jewelry! They even went and sold or pawned some of it on Dec. 14, and later that evening he was wining and dining Amber.
I read on one of the recent timelines here that she shared the $$$ form one of the sales with Amy.
Another $$$ angle... I remember an old Doris Day movie I saw as a kid, where her husband was missing for 7 years, he was declared dead, she remarried, then husband #1 returned. What a mess! But funny. :-)
What if Scott wanted her dead BUT MISSING, so that her estate would stay with him, as her next of kin? She was going to get a million dollars from the sale of her grandmother's house (or 1/3 of that million). If she's reliably eaten by the fishes and crabs, it would all go to Scott after 7 years.
I can't but help think that that lends an additional motive to his dropping her into the Bay.
Your endless lists of questions fleshes out those nagging thoughts about no one else doing it. Thanks for having the patience to type it all out!
Pinz