I called and tried to split my upcoming PNR, but was told it wasn't possible because I booked via Delta Vacations. The Delta phone rep recommended I buy a one-way ticket for me and leave the original reservation alone. The new one-way was less than the price of the change fee.
I am now returning to MSP from LAS 10 hours before DH. Hopefully he won't have any issues when he gets to the airport! Too bad I can't get MQMs for both flights!