What is the ruling on one who used tissues for Istijmar and did not remove the impurity from the toilet seat for fear of his clothes becoming defiled by splashing water, and is expiation obligatory for him because of that, given the long distance from the park?

The questioner is warned against succumbing to obsessive whispers (waswas), as they lead to great evil. They should know that the basic assumption about a place is that it is pure, unless one is certain of the presence of impurity. No attention should be paid to the obsessive whispers about the presence of impurity, and there is no obligation to purify the bathroom from any remaining impurity within it.