The 800p looks to be wide open. You could SDC onto it; it's risky though given that you can't change onto it until 3 hours before its departure - which is after your MEM flight leaves.

The 455p connection via IND looks real full, as does the 445p to SLC. The 435p to ATL also looks pretty full. It's more of a problem of getting out of CVG than it is getting to LAS.

FWIW, your CVG-MEM flight is sold out. Zsmith2 (a DL Connection GA) mentioned the other day that there is a new policy in place that if a passenger is on an oversold flight, GAs have the latitude to move them to earlier (open) flights. The 855a nonstop flight looks pretty open, and the 220p to SLC looks relatively open as of right now.