Question back to you one Are you on a paper ticket?

-Point two, that routing is terrible, although lots of miles. Is that the best that Delta could pull or did you have to get creative with your TA?

1. I doubt that you will be able to BUMP over to NW at SEA coming from an international flight. You are, however, technically on a full fare (although discounted ticket). What I would probably try to do is go to NW's counters at ICN and see if they will take your ticket and allow you to fly ICN-NRT-DTW-Stopover-SAT. Heck it might work!

As an aside, the first question I ask either of my two somewhat incompetent government issued travel agents is whether NW matched a fare. You can fly on the matched fare after making a pretty simple business case. My personal favorite one is, "Connecting through ORD significantly increases the risk of misconnect"

3. Sure, if somehow this got pulled off you would be eligible for domestic upgrades.

4. Looking bad SAT-MSP, only 7 F seats total left for sale before the Plats are run. Fighting chance MSP-SFO.

5. Fighting Chance, Ouch, Fighting Chance.

Hope this helps somewhat.