Either way, Japan and Korea are next door. The OP could earn roughly 750-800 EQMs/RDMs each way best case scenario. Obviously that is not worth $800+. For $800 you could go from US48 to Europe and earn up to 12K roundtrip. 1,600 VS 12,000? Obviously paying $860 should be your last option because if you take the cheaper flight you save around $430 and still get to keep your 60K+ miles.

As far as paying 62.5K miles.. obviously that's another hoax. For 60K you can go from Asia to US48. But in this case you're using the same amount of miles to travel from NRT-ICN, which is about the same distance as SFO-SEA. You can get to Japan via boat from Korea, so why pay the cost of traveling to another continent?

Best bet is to fly Korean Air. The fare class likely would be eligible for mileage on DL given the price of the ticket, and if not, then frankly, save yourself all those miles and dollars and start shopping for another carrier which doesn't rip off their customers.