OP, I wonder if you had an update on what you decided or discovered in your situation.
The Lat FP is looking attractive for an upcoming ticket, fare-wise and upgrade-wise, other than the return trip timeframe. The stopover at the AC city and train to destination is fine on the way there, but coming home, I have less time for the repositioning and it would have to be air. I've never used my cc (TD First Class Travel Inf) for trip interruption but it appears to cover economy fare to next destination (boo, if I've upgraded) if due to mechanical or weather - but not outright cancellation. (The covering insurer provides only a phone number, no accessible means for me to contact them, which raises my temperature a little.) Not sure how Amex Plat compares to that.