Not with Africamper directly. The Insurance Excess is ZAR / N $ 8000. You could however take out travel insurance (rental protection) in your home country, which will reimburse the excess in the event of a claim.
Yes, the Excess is debited in the event of a claim until it is determined who is guilty. Accordingly, the Excess might be refunded. Unfortunately this assessment of the Insurance company can take several months.