Is refraining from consuming products containing certain symbols (such as E120, E330, and soy lecithin) due to the belief that they contain pork fat considered a legitimate act to avoid doubts and escape the forbidden? And will one be rewarded for their intention if what they read was incorrect? And is it permissible to buy questionable products, such as soft drinks, based on a parent's request?

What the questioner mentioned is merely an unsubstantiated report. The general rule for foods is permissibility and lawfulness until proof of prohibition is established. If you avoid questionable products, you are on the right path, for the Prophet, peace and blessings be upon him, said: "Leave that which makes you doubt for that which does not make you doubt." Nevertheless, as long as the authenticity of the report is not confirmed, there is no harm upon you in obeying your father by purchasing them. As for claims of the presence of pig fat in common products, this requires evidence from an accredited source, and the general rule for things is permissibility.