The resurrection being fictional explains assertions 1, 2, and 3 quite handily.
None of those 3 things has ever been established "outside of any appeal to biblical authority". But I'm particularly curious about 2. You think that there is a reason outside the bible to believe “The disciples had experiences that they believed were the actual experiences of the risen Christ.”? I’m curious as to what your reason for thinking that is.
And the empty tomb is just part of the resurrection claim. It isn’t really data that needs to be explained. That the people who claimed Jesus rose from the dead also claimed his tomb was empty is a detail that should surprise no one and tells us absolutely nothing of whether the claim is true.
The only reason why anyone would think there was an empty tomb is because they believe the accounts in the gospels are accurate. That is to say they think they believe in the accuracy of all four accounts of the empty tomb. No one person could simultaneously believe the events of all four accounts. And not more than one account could be true. And that can be arrived at from a position which accepts the possibility of Jesus’ resurrection. Just reading the four accounts inescapably confirms that at least three of them are lying.
Who discovered that Jesus’ body was not in the tomb?
Matthew (28:1): “In the end of the sabbath, as it began to dawn toward the first day of the week, came Mary Magdalene and the other Mary to see the sepulchre.”
Mark (16:1): “And when the sabbath was past, Mary Magdalene, and Mary the mother of James, and Salome, had bought sweet spices, that they might come and anoint him.”
Luke (24:10): “It was Mary Magdalene and Joanna, and Mary the mother of James, and other women that were with them, which told these things unto the apostles.”
John (20:1): “The first day of the week cometh Mary Magdalene early, when it was yet dark, unto the sepulchre, and seeth the stone taken away from the sepulchre.”
Was the stone still there when they got to the tomb?
Matthew (28:2): “And, behold, there was a great earthquake: for the angel of the Lord descended from heaven, and came and rolled back the stone from the door, and sat upon it.”
Mark (16:4): “And when they looked, they saw that the stone was rolled away: for it was very great.”
Luke (24:2): “And they found the stone rolled away from the sepulchre.”
John (20:1): “The first day of the week cometh Mary Magdalene early, when it was yet dark, unto the sepulchre, and seeth the stone taken away from the sepulchre.”
Were there angels at Jesus’ tomb? Where they actually angels or just men? Was there one or two of them? Were they inside or outside the tomb? Were they there before Mary (and pals?) arrived or did they appear after?
Matthew (28:2): “And, behold, there was a great earthquake: for the angel of the Lord descended from heaven, and came and rolled back the stone from the door, and sat upon it.”
Mark (16:5): “And entering into the sepulchre, they saw a young man sitting on the right side, clothed in a long white garment; and they were affrighted.”
Luke (24:3-4): “And they entered in, and found not the body of the Lord Jesus. And it came to pass, as they were much perplexed thereabout, behold, two men stood by them in shining garments.”
John (20:11-12): “But Mary stood without at the sepulchre weeping: and as she wept, she stooped down, and looked into the sepulchre, and seeth two angels in white sitting, the one at the head, and the other at the feet, where the body of Jesus had lain.”
What (if anything) did the man/men/angel/angels say?
Matthew (28:5-7): “And the angel answered and said unto the women, Fear not ye: for I know that ye seek Jesus, which was crucified. He is not here: for he is risen, as he said. Come, see the place where the Lord lay. And go quickly, and tell his disciples that he is risen from the dead; and, behold, he goeth before you into Galilee; there shall ye see him: lo, I have told you.”
Mark (15:6-7): “Be not affrighted: Ye seek Jesus of Nazareth, which was crucified: he is risen; he is not here: behold the place where they laid him. But go your way, tell his disciples and Peter that he goeth before you into Galilee: there shall ye see him, as he said unto you.”
Luke (24:5-7): “And as they were afraid, and bowed down their faces to the earth, they said unto them, Why seek ye the living among the dead? He is not here, but is risen: remember how he spake unto you when he was yet in Galilee, saying, The Son of man must be delivered into the hands of sinful men, and be crucified, and the third day rise again.”
John (20:13): “And they say unto her, Woman, why weepest thou? She saith unto them, Because they have taken away my LORD, and I know not where they have laid him.”
What did Mary do after she talked to the men/angels?
Matthew (28:8): “And they departed quickly from the sepulchre with fear and great joy; and did run to bring his disciples word.”
Mark (16:8): “And they went out quickly, and fled from the sepulchre; for they trembled and were amazed: neither said they any thing to any man; for they were afraid.”
Luke (24:8-9): “And they remembered his words, and returned from the sepulchre, and told all these things unto the eleven, and to all the rest.”
John (20:14-15): “And when she had thus said, she turned herself back, and saw Jesus standing, and knew not that it was Jesus. Jesus saith unto her, Woman, why weepest thou? whom seekest thou? She, supposing him to be the gardener, saith unto him, Sir, if thou have borne him hence, tell me where thou hast laid him, and I will take him away.”
So some key details of the empty tomb claim appear in up to four conflicting forms. Since we know three of the gospels must be wrong, how can we know who is right? What extrabiblical source of the empty tomb story would you suggest we use to weigh this disagreement between the four gospels?