Does one break his obligatory fast by intending to break it due to an intrusive thought, and is one considered to have nullified his ablution if he intended to nullify it then resumed completing it?

If a person intends to interrupt an act of worship while performing it, it becomes invalid, except for Hajj and Umrah, which are not invalidated by the intention to interrupt. In prayer and fasting, interrupting the intention or hesitation invalidates the act of worship, contrary to the opinion of Ibn Uthaymeen regarding hesitation. As for a mere passing thought, it does not invalidate the act of worship. If one intends to interrupt ablution (wudu'), what has preceded of it becomes invalid, according to the soundest view of the madhhab. And one must be cautious of obsessive whispering (waswasah).