What is the ruling on dryness and the white substance in the navel, protrusions in the ear, and the white, flaky substance that forms when peeling the skin after cutting the nails, if these are considered barriers preventing water from reaching the skin?

It appears you are experiencing obsessive thoughts (waswas), and we advise you to disregard them and not pay attention to them. Dirt originating from the body, such as secretions, is not considered a barrier [to ablution]. Even if it were considered a barrier, and you were certain of its presence before ablution, you could adopt the view of those who pardon minor barriers unconditionally.