Is what the questioner does, in terms of exaggerating purity and the resulting hardship and constriction in his life, considered an uncalled-for religious extremism?

Obsessive doubts have taken hold of you, and the solution is to ignore them and pay them no mind. The water you use for istinja' (washing after relieving oneself) is pure if it separates from the impurity after removing it, or if it has not been altered by it, or if you doubt its contact with impurity. The default state of the water on the bathroom floor is purity, unless it has been altered by impurity. And the water that separates from the body during ghusl (ritual bathing) is pure. All these matters are obsessive doubts that must be repelled and not indulged in.