If you insist on booking the two tickets into the same PNR, you will both be booked into the cheapest fare bucket which has at least 2 seats remaining.

Book the first ticket in whatever the cheaper fare bucket is and then go back and book the second ticket into the cheapest fare bucket available. You may even find that the second ticket books into something between #1 and what you were finding for 2 tickets.

This has zippo to do with DL or Thanksgiving.

If there is better pricing on AS and AS provides you with acceptable convenience, why on earth book anything else?