The word you want is “confabulation”. It is the fabrication of a story that sounds slightly feasible, but holds no basis in reality. Confabulation is a symptom of severe dementia.
At this point, it’s not willful lying, it’s that his brain is so much mush that he has no capability to discern his stories from actual fiction.
As usual, every accusation is a confession. Every “Sleepy Joe” story was him projecting his concern that he is mush onto his enemy.