Thanks,
Often1 and
PointsPanda, your insights/advice echo my experience so far. I did send some exec emails, and made one more attempt at customer service - and got totally useless refusals.
I also started the DOT complaint (yesterday), though I don't have much expectation of that, on it's own, doing something.
I also started a chargeback, since it had been far longer than 7 days since AM's initial refusal to refund. So, that money at least has been returned (temporarily - will hopefully stick).
The "suggested" schedule was no good at all - my arrival switched from early afternoon to middle of the night, and my departure flight moved from early morning to middle of the prior night - the changes would've cut two days from an already short trip.
The funny thing is, I would have likely used a voucher, fairly quickly - I'm looking at a trip to PVR in just a few weeks. But there are so many horror stories about using the credits, it seems like the refund/chargeback is the safer option.