Thanks again for all the help. The routing became available for 3 weeks later, and I was actually able to book it for slightly under the Expedia price.

If anyone else wants a cheap run MSP-AMS for $410, these are the flights, or maybe you can work out something from elsewhere:

5/22 CO 171 MSP-EWR
5/22 CO 96 EWR-TXL

5/23 CO 9726 TXL-AMS (KL 1822), Continental.com support must insert this one

5/24 CO 103 AMS-EWR
5/24 CO 370 EWR-MSP