Yes, the continent of origin is counted as a continent.

I believe you would have to use the Visit Europe pass either before leaving Europe for Asia or after returning from the last intercontinental RTW segment. As you note, you are subject to the in transit rule when passing to/from Africa via Europe. Also, I think this Europe-Asia-Europe-Africa-??? might be considered backtracking or violate the one in transit per continent rule unless you can get out of Africa without going back through Europe.