Is it permissible to adopt Ibn Taymiyyah's view that a small amount of impurity is absolutely excused, including what affects food, in order to overcome obsessive doubts, especially after a hand contaminated with oil and soap residue, which might be impure, touched the toilet seat, leading to the contamination of cooking utensils and food?

The obsessive thoughts have reached their peak with you, and there is no cure for what you are experiencing except to completely disregard these obsessive thoughts and not pay any attention to them. The soap you used to wash your body is not ruled to be impure unless you are absolutely certain—a certainty you could swear by—that it has been mixed with impurity. And you have washed the toilet seat more than once; so, even if the soap was impure, the seat would have become purified by washing it afterwards. This impurity is among the minor impurities that are excused by the majority of scholars. There is absolutely nothing that necessitates this hardship. And if scholars differ on an issue, there is no harm for you in adopting the easier opinion.