I'm on a paid BE int'l ticket, Mr. Marylou is on a mid tier award at 200k miles, itineraries linked.

A health issue has arisen that could possibly cause us to have to interrupt our trip and return early. How would that affect the award ticket if there were no mid tier seats available on the return?

To get the "last seat", would we have to pony up the full difference (150k) or 75k for the half that we haven't used?

Also, to get the flight we wanted, I was forced into an O fare on the return. What are the change rules on that fare?

I guess I'm trying to decide if it would be better to just cancel the whole trip now to avoid a big hassle if we need to rush back home.