Thoughts on:
(1) $4500 title loan: This is merely the money we know about. I highly doubt with the presumed amount of planning on TC's part that this is the sole amount of funds that they're travelling with. At 50 years old, TC would know that even with an off-the-grid lifestyle, $4500 wouldn't be sufficient even in the short-term.
(2) Instagram posts: I keep looking at his posts - the giant tooth picture posted 1W ago (or thereabouts as we know they've been gone for nine days as of today) is hashtagged #dentistonmonday. I'm wondering if this was the Monday that he picked her up and if so, if the hashtag was code to her regarding the plan or was it the complete opposite? Like an alibi for why he'd have to leave the house on what was reported as a day off from school?
Also, the hastag #ohtheplaces (seen on a pic of Costa Rica) is an obvious reference to "Oh the Places You'll Go", the Dr. Seuss book. IMO, he made promises to ET that they could life a happily-ever-after life together as a married couple in a warm, tropical setting (ET would of course, not know the reality of why the marriage could never be legal). And that sure, maybe it would be tough at first for them as they'd have to rough it a bit before getting to their matrimonial paradise but that in the end, it would all be worth it as they'd be together forever in a beautiful setting and far away from her abusive past.
In other words, he manipulated her with these far-fetched promises and what's even worse, I think he actually believes in this fantasy scenario as well.