You can sometimes get the exact flights you want by doing the advanced search with multi city, although sometimes you must use the search by schedule function to piece the trip together. The disadvantage of this is that you do not see the fare codes or prices until the end, although you can usually first identify the availability and prices on the segments separately.

However, to save time, I usually just call the DM line and tell them what I want after I have looked at the schedules. Nonelites doing it this way pay phone booking fees and risk getting incompetent and lazy agents when they call.

It could be worth paying a real human travel agent their ticketing fee, probably about $35, to get the ticket. A real TA, NOT an online operation, can do more to control whether the flights are booked as codeshares and what ticket stock is used. They can sometimes also do things like writing separate tickets with part exEU when this saves money.

However, I wonder whether your plan makes sense. I would not connect through JFK or ATL when a nonstop directly into MSP is available. If you must connect, pick DTW. If you have GE, pick an airport that has this system to go through customs and immigration if you do not use the MSP non stops.