If the rabies antibody titre is >0.5 iu/ml which is considered protective, is it enough to protect any amount of rabies viral load??

No guarantees: The WHO guidelines (>0.5iu/ml) require higher levels than the CDC guidelines, but neither guarantee this is protective in all situations. There other person specific immune factors that may make it less valid as a guarantee in all exposures. This level is the bottom amount considered generally protective for those in high risk professions.