1) Yes, the top priority is getting rid of the Zuptas
2) However, I doubt they are responsible for 99% of government corruption. There are too many independent tendrepreneurs for that at municipal, provincial and national level; responsible for a large share (30%? 50%? 75%?) of government corruption
3) Without huge changes in SA, other tendrepreneurs will rush in to fill any gaps left by removing the Zuptas. 
4) The good guys in the ANC (Jonas, Gordhan, Motsoaledi, Ramaphosa, etc.) won't be able to clean up the ANC, even if their faction wrests power from the Zuptas. Compromises with the ANC corrupt will be unavoidable. They should vote against Zuma in the vote of no confidence, and after his fall and the fall of the cabinet, leave the ANC and form a new party, or join existing opposition parties. Then an opposition coalition can wrest power from the ANC at the ballot box. This is our only chance of getting clean government; attempts to reform the ANC will have no or limited success.