Does one sin for adopting the view of Ibn Taymiyyah that it is not obligatory to use water for istinja' when the impurity has spread beyond its original place, in order to alleviate the WASWAS (obsessive doubts) of purification and the hardship of istinja'?

Obsessive doubt (waswasah) is a chronic disease that corrupts both religious practice and worldly life. The cure for it is to ignore it and pay no attention to it. As long as your feeling of urine spray is an obsessive doubt, do not pay attention to it. Rather, proceed with your worship until you achieve complete certainty about the presence of impurity. Indulging in obsessive doubts is a cause of distress; if you were to ignore them, Allah would remove this worry from you. What is attributed to Sheikh al-Islam concerning the permissibility of using stones (istijmar) even if the impurity has exceeded its usual place is correct, but what the questioner mentioned is not what the scholars intended by "the impurity exceeding its usual place."