Yes, they will waive the fee, that doesn't come into it with involuntary changes. I think I've seen reports where the scope of available flights changes after a few days. I've looked at 2 May and I agree that there doesn't seem a reason why the other 4 flights are not opened to you, unless perhaps there is a point of sale issue or other oddity involved. But if you now know which flight to take, I would just ring up. We know the disruption menu doesn't show all options open to you (e.g. the 350 mile rule).