First, he needed his handcuffs in front of him, not behind him.
This is gonna hurt, he thought wistfully to himself, tipping his chair backwards. He winced as his back crashed into the ground. Curse my relative tallness!
But from here, he could shimmy his legs and torso between his arms and end up with the chair (and handcuffs) in front of him. Coming to a standing-crouch, Shelton dragged the chair up and over to the table.
Some sort of experiment sat on the table. He didn't care what it was. Delivering it an awkward kick, he sent the materials scattering over the floor. Picking up a snapped wire, he released the latch on his handcuffs.
"Damn, I feel like MacGyver," Shelton muttered to himself, in awe at how far he'd gotten.
Other than the thin wire, the only surviving useful piece of the device was a small propane tank. Shelton pocketed it and turned to the door.
The guard had destroyed the lock, but the door could still be opened if he could stimulate the wires in the wall that led to the door lock. Shelton remembered where the lock was on the other side. He needed to burn through the wall, and it would be thinnest and weakest where the lock used to be.
Using the thin wires to pick the keyholes, he raided the cupboards, and used a battery and steel wool to light a fire, which he used with the propane burner to heat up the thin section of wall. When it was hot enough, he punched through with an aspirator.
Reaching through with his hand, he found the damaged ends of burnt wires. Using a rubber glove, he felt which wire seemed to come from where. He needed to stimulate the right one. Once he was sure he had it, he built up static electricity and touched the wire with the end of a sliver of metal. The spark shot though the metal and stimulated the door lock. The door slid open.
The hallway was deserted. Shelton waited for the security camera to look the other way, then darted into the next lab.