Is it obligatory to repeat the Dhuhr prayer if dirt is found stuck to the face an hour after performing ablution, knowing that one suffers from excessive whisperings (waswas)?

What you find on your face after ablution, if it does not prevent water from reaching the skin, then the ablution is valid. If it does prevent water from reaching the skin, then it should be added to the nearest possible time. Your prayer is valid and you do not need to repeat it. It is recommended to disregard obsessive thoughts and not pay attention to them.