What is the ruling on doubting the sufficiency of the money allocated for charity for those from whom it was stolen, and is it obligatory to compensate for this shortfall?

As long as the questioner's repentance is accepted and he cannot reach those whose rights are owed, then he must give charity on their behalf what he owes them and strive to estimate the amount to clear his liability. As for his doubt whether he gave that amount in charity to the worker with the intention of giving it on behalf of those whose rights are owed, his liability is certainly occupied with those rights and is not cleared by doubt.