ANA plus CO, and yes.

I initially searched ANA for FRA-ORD knowing that there are a lot of flights and that LH is generally generous with inventory. I do not wish LH Y on even my worst enemies, but it is often available and it is a place to start. That had no inventory so I next searched ARN-YYZ knowing that AC has a great TATL Y product and often has lots of inventory. They didn't have anything on this flight, but ANA showed connections via LHR with the SK flight open. Once I had that I went to co.com to search for LHR-ORD since CO includes VS flights when they are available and VS does fly that non-stop and you can mix *A and VS on the same award with CO OnePass miles. VS wouldn't be my first choice in Y but it is better than LH and skipping the connection would be worth it if you could. VS wasn't available and neither was UA's non-stops but co.com did show the CO+UA flights as available.

My guess is that in the coming weeks you can optimize the itinerary and get better connections, shorter flights or other improvements. As long as you are outside of 21 days from the date of travel (i.e. until 3 July) changes to that return are free so long as you leave from ARN and arrive at ORD eventually. You can even ask the agent to waitlist you on the CO ARN-EWR plus CO EWR-ORD to make it easier should the seats open up. But you need to have something confirmed before you can waitlist a better alternative.