If you are going to Malawi, you want to start on a new one, rather then try desperatly find new one somewhere in northern Moz if things don't go to plan. This kind of tyre life stretching is fine in places where the tyres are readily available, but north of Namibia, you are on your own.
It is easy really - bring and change both of your tyres in Nam. If your current is still fine, just leave it with your father, and once you are back, swap it back.