brother asked ''I lead my parent in salah. Many times i recited certain surahs from memory even tho im unsure about a letter in an ayah (for ex: س or ض) but continue past it to ayat im sure about. Mistake is due to me neglecting revising it or forgot to. Do i repeat all those salah? Maybe 50-100+''

Ustadh AbdulAziz al-Haqqan

This is a very obvious waswas also the 2 letters u mentioned are not close so how? If it is not in the fatihah, u do not need to repeat anything. And i believe from your question that it is not the fatihah.