Is the worshipper's feeling that he is the imam when rising from bowing considered a change of intention and invalidates the prayer? And is ablution considered valid if the hand dries during wiping the head except for one finger with which the wiping was completed?

One must beware of intrusive thoughts (waswas) and not succumb to them. What occurs to the worshipper, such as an illusion of changing the intention to lead the prayer, or a dry finger when wiping the head, are mere intrusive thoughts that have no effect on the validity of the prayer. It is sufficient for a woman to wipe part of her head according to many scholars.