How can one differentiate between an affliction from God and a satanic whisper that incites to disobedience, especially since lying and sodomy have been mentioned as afflictions?

There is no contradiction between Satan beautifying sin and Allah's decree of it for a profound wisdom, such as testing a servant to repent, or as a punishment for a previous sin. It is incumbent upon the servant to repent and increase in good deeds that expiate sins. It is not permissible to use Allah's decree as an excuse for committing sin, because Allah has clarified good and evil and has given the servant power and will. Citing predestination as an excuse is a false argument, like the argument of the polytheists. The servant must repel the decree of sin with repentance, just as hunger is repelled by eating.