Does urine splatter from the toilet seat onto the body while urinating in a sitting position, and what is the ruling on water splattering during istinja' (cleansing oneself after urinating or defecating)? And what should the worshipper do if the imam bows before he completes reciting Al-Fatiha?

The summary of the answer:

Wasaawis (obsessive whispers) should be ignored and turned away from. Doubt about urine contamination is considered as non-contamination. Doubt about whether something that has touched you is pure or impure is considered as pure. Water splattered on the body is considered pure unless its contamination with impurity is certain. In Istinja (washing after relieving oneself), a strong presumption that the impurity has been removed is sufficient; certainty is not required. The prayer of the congregant is valid if the Imam bows before the congregant completes Al-Fatiha, and the congregant should complete it even if the Imam rises. This is the relied-upon view among the Shafi'is.