You seem to be trying too hard to rationalize events you would never entertain for any tradition other than Christianity. Ask yourself honestly why that is.You refer to Matt. 27:
"the graves were opened; and many bodies of the saints who had fallen asleep were raised
And came out of the graves after his resurrection, and went into the holy city, and appeared unto many."
I recall a tradition outside the Bible that 2 sons of a high priest reenlivened at this time. Unfortunately, I don't remember the details.
One problem with proving or disproving the verse in Matthew is that it doesn't give more details about this incident. It makes it sound like dozens of graves physically broke open within a few days after Easter Sunday, walked into Jerusalem and were seen by dozens.
However, closer analysis raises questions like whether the physical graves broke open physically and literally, or if the grave opening refers to a transformed spirit body rising through a closed grave. If it means the former, then who if anyone witnessed the grave literally opening?
Depending on the details of the event, Josephus might not have included it, considering the event to be unsubstantiated visions.
If you are looking for stronger counterarguments to the Resurrection of Christ, let me point you to my thread on the topic.
On another thread, I listed the most direct arguments in favor of Christ's Resurrection. (https://forums.carm.org/threads/a-list-of-the-strongest-most-direct-evidence-for-jesus-resurrection.361/) In this thread, I am doing the converse- I am listing arguments that it did not occur, as well as...forums.carm.org
You missed the strongest counterargument to the resurrection of them all... They just do not happen - ever.