Bag of Holding ‘bomb’ and Immovable rods

Scenario – My PC was faced with an unwinnable battle and decided to cast invisibility, sneak up the lead bad guy, toss a bag of holding into another bag of holding, essentially clearing out a 10×10 space of bad guys, including the leader.

Now here is the contestable part – The PC that essentially executed the ‘bag bomb’ placed two immovable rods tied to a rope of climbing to keep in the current plane and not be sucked into the Astral plane.

As the DM, I am struggling with – Does the Bag of Holding inside a bag of holding cause a force blast into the Astral plane or is it a teleportation – ‘blink and you are gone’ kinda of experience? Depending on the answer, then did he and the rods all get sucked or teleported through? Do I require a strength check to see if he held on and if so, vs what DC? Would the force of the ‘sucking’ be so great that he suffers damage? What would be the damage? Would he lose all of his belongings on person?

Help please!