Sorry, I don't have any simple ideas for how you can get free WorldClubs admission even if you are flying a lot in one day. First class travel doesn't get you into the WorldClubs for domestic travel.

One thing, though -- you might want to recompute your mileage. You get a minimum of 500 miles per segment so your PNS-MEM-ATL run is worth 1000 miles each way (plus bonuses). That should push your total over 18,500!