Plot hole: It appeared there was ample time for Milo to apply the so much desired 'cure' that Michael warned him about. Milo is no doctor and did not witness Michael's application procedure. Milo could have never known the precise way to perform the risky procedure, let alone he had assistance from anyone other than Martine.
Plot hole: Vulture from the MCU is pulled into the Venomverse due to the spell cast by Doctor Strange in No Way Home. This is absurd. The first spell pulled characters from other universes into the MCU, while the second spell brought the characters back to their proper universes. Neither of these spells involved pulling characters out of the MCU and into the other universes. Vulture of the MCU was already in his proper universe. No explanation is provided for this.
Plot hole: Vulture was able to re-create his suit despite the tech for it being confiscated when he was arrested. Also, the tech does not exist in the Venomverse, so he would have had no means of accessing it by any stretch of the imagination.