Is what happened considered a delusion (waswasa), and does looking at the leg of the fiancée's mother—mistaking it for the fiancée's leg—affect the marriage in the Hanafi school of thought, and is the prohibition in the Hanafi school of thought limited to looking at the private parts only, or does it include other parts, and is marriage to her valid in all schools of thought?

The viewing that establishes the prohibition of affinity according to the Hanafis is looking with lust at the private parts and nothing else. The prohibition of affinity is not established by looking at other body parts with lust, nor by touching other body parts unless it is with lust, without any dispute. The questioner is advised to turn away from whisperings (waswas (definition)) and not pay attention to them.