Good points.
Watch how much info comes out about this guy. If any.
How long does it take for ebola to kill someone; would he have at first been strong enough to walk on the plane yet later have the rapid decline and violent symptoms?
Ebola is not terribly rapid, no. It takes several days — up to about two weeks — to progress from feeling ill to either recovery or death. One of the things that makes Ebola so terrifying is that it is a lingering, horrific death.