I've done MSP-ICN-SIN as well as MSP-NRT-SIN earlier. The schedule through ICN is much better in terms of departure and arrival times in SIN.

Be careful if ICN-SIN is still considered a "regional" route for KE (which would mean business class lite) and especially avoid aircraft with 2-3-2 seating in business class. In fact, check all KE seat maps if you want 100% direct aisle access. I've had several bad experiences with KE changing my J aisle seat to a middle. If an aircraft is used that has an F cabin sold as J, as a DL customer, don't expect to be able to beg for one of the better seats (which will be given only to KE customers, even those without any elite status).

My suggestion would be to consider JFK-LAX-ICN in D1 connecting to ICN-SIN on KE. If JFK-SEA is D1 on your travel dates, connecting through SEA but doing DL TPAC might be another option, although the D1 lounge at LAX would be an argument in favor of that routing. [I haven't tried to check schedules.] Does DL operate a JFK-ICN nonstop? [You only mentioned JFK-ICN on KE in your OP]

Some people here praise service on KE, but I find it too obsequious for my taste and sometimes outright sexist. I also find it irritating that KE shows such obvious preference for their own customers, such as booting a DL elite from a reserved seat just because a KE passenger has requested it (in the absence of considerations such as seating a family together or a handicapped person needing as aisle seat).