How can a husband bring his wife to orgasm by caressing her genitals if the place becomes ritually impure with madhy (pre-seminal fluid), knowing that it is not permissible to directly touch a ritually impure place, and how does this also apply to oral sex, where madhy is emitted from the very beginning?

The fundamental principle is the obligation to avoid impurity (najāsa) and the impermissibility of touching it, except out of necessity (ḍarūra) or need (ḥāja). If avoiding impurity becomes difficult during intimate relations, then it is hoped that this constitutes a need that permits touching the impurity.