Status on Airline A is no help with Airline B.

And, yes, in the winter months I would be worried about a one-hour connection at IAD. Remember that you are supposed to be boarded and strapped into your international leg 30 minutes before departure. Even if your ORD-IAD arrives exactly on time, if you're sitting in the back of the plane, that gives you 15 minutes to make it to your next gate.

I would pay the change fee to move to an ORD-IAD that gets you in three hours before the international leg leaves. That way even if it runs two hours late, you're cool.