How can one differentiate between the verses (or signs) that occur to the heart as a form of intimidation from Allah due to sins, and those that come from Satan? And what is one obligated to do if these verses are from Allah?

Satan does not mention Allah or His verses; rather, he enjoins immorality and evil. The verses that you remember, which instill in you fear of Allah Almighty, may be from an angel's inspiration, a thought within yourself, or a divine inspiration from Allah. This is a great good that should be utilized by abandoning prohibitions and performing enjoined acts, which will increase faith and steadfastness in the truth.