This one is simple. It is a departure from the EU and thus EC 261/2004 applies. If the flight is cancelled, OP may elect a refund. If the OTA refuses to process a refund, OP will need to make a perfunctory request to AM. If the refund is not issued promptly (7 days), OP can then initiate a charge back through his card issuer (bank). This will get taken care of in short order.
But, don't waste time here. Make the request(s) and then move to the chargeback.