Is it obligatory to wash the entire house after experiencing obsessive doubts (waswas) about the impurity of semen on the hand, and subsequently touching various parts of the house with that hand, and is invisible impurity excused?

What your hand touches does not become impure if semen gets on it, because semen is pure according to the majority of scholars. You must repent from masturbating because it is forbidden, and you must cast away and strive against these whispers [of doubt].