You can cut much faster with the PC router that you are using.
Try the roughing pass at 18,000 rpm and 300ipm.
Then do a single finish pass at 18,000 rpm and 250ipm.
That should reduce the time substantially.
The wood is cupping because it's drying. If you want it to stay flat, it needs to be kiln dried to 6-8% moisture before you machine it. If you don't live in a desert, you'll only see this immediately after removing it from a kiln. Note that construction pine is not usually dried that much, even when it's kiln dried, it's usually closer to 20%.
A PC7518 has more than enough power for these light cuts.