Is earwax that has transferred from the ears to the hands and then to the feet during ablution considered a barrier that prevents water from reaching [the skin], or is it sufficient to wash it with water only despite the persistence of its traces? And is it permissible to interrupt ablution to wash the hands with soap to remove the wax and then resume it?

Wiping the ears is a Sunnah (definition), not an obligation. This involves wiping their outer and inner surfaces without exaggerating the insertion of the fingers, and any method of wiping is sufficient. The residue remaining on the fingers from wiping the ears does not affect the ablution (Wudu), and it is not necessary to wash it with soap; wiping it with a tissue is enough. This has no relation to washing the feet, as the water reaches the feet before the hand passes over them. One must beware of obsessive doubts (waswasah) and turn away from them, as well as from extremism and exaggeration.