The problem is that you are entering Europe twice. You can only do that if one of them is in to or from Ghana, Nigeria or (now) Kenya.

There are three ways in and out of JNB: to Europe, to Asia (CX to HKG) and to SWP (QF to Sydney). You need to take one of them on the way in and a different one on the way out, or you need to go overland from JNB to Ghana, Nigeria or Kenya, and then you could fly out from there via LHR.

To go to the places on your list you would need to route:

ist-lhr-dxb-lhr-jnb-hkg-nrt-hkg-del-hkg-jfk-sfo-dfw-anc-dfw-sjo-lax-lhr-ist

and you have two spare free segments to use in Africa if you wish (or two paid extra in one of the other continents)