Kadmiri claims in the lawsuit he was beaten for 20 minutes at the Excalibur by SPI employees and Thunder From Down Under members and hotel security destroyed or concealed video of the attack.
Kadmiri also claims he has suffered cramps, flashbacks, blackouts, difficulty breathing, memory loss, headaches, extreme anxiety and pain in his jaw since the incident.
Kadmiri has been charged with robbery with a weapon, burglary and battery.
The prosecution has been on hold since September as Kadmiri's mental competency is reviewed.
At earlier court proceedings, prosecutors described how the Australians were midway through a show at the Excalibur on March 18 when some members allegedly confronted Kadmiri backstage.
He allegedly stole props and put on a pair of teal underpants and a G-string used in the show.
In a scuffle, Kadmiri pulled out the Magnum revolver and fired a bullet, narrowly missing a member of the crew in the face and hitting the wall of an Excalibur restaurant, the court was told.
Thunder From Down Under and Excalibur's owner MGM Resorts International declined comment on Kadmiri's lawsuit.
-AAP