How did he get the disease? Sharing fluids with a sick person? Something about this doesn't make sense. If you can't get this from someone who isn't showing symptoms, there must be a lot of people sharing body fluids with Ebola patients in Africa.
Infected person is relatively safe while no symptoms have been developed. However, infection through blood transfusion or sexual intercourse is still possible.
All you need to do if swap bodily fluids, it does not need to be as much as you would get from sex or a blood transfusion. It can be as little as a little bit of blood, vomit or feces
Only if person developed symptoms of the desease. Don't forget that saliva and perspiration also contain antibodies which are capable to neutralize the virus particles. If there are no symptoms then there is not enough virus titres in the fluids to get infection. But the blood and semen, on the other hand, have very high titres of virus even if there are no symptoms developed yet.