Is the questioner considered legally responsible for any harm that may befall a person inside an ambulance, due to his unlawful stop and obstruction of traffic, and the consequent potential delay in the ambulance's arrival? And is he obligated to inquire about the patient's fate? And does the ruling apply to all other cars that obstructed the ambulance?

There is no sin upon you, nor are you required to ask about what you mentioned, for these are whispers (waswas) that should be ignored. The effective cure for waswasa is to completely ignore it and not pay any attention to it, for it will disappear after a short time. Whoever indulges in it will be led to the realm of the insane, as stated by Ibn Hajar Al-Haytami. Whoever is afflicted with waswasa should seek refuge with Allah and stop; because it is from Satan, whose only goal is to lead the believer astray. Whoever contemplates the ease and clarity of the Sharia will be rid of the disease of waswasa. Waswasa afflicts the ignorant, but whoever possesses true knowledge and intellect will not deviate from following (the Sharia). It is recommended for one afflicted with waswasa during ablution (wudu) or prayer (salat) to say: "La ilaha illa Allah (There is no god but Allah)."