The regulator freezing is because of the leaks. It will stop when you get the leaks stopped.
First take off your tank
1 Turn your regulator all the way down.
2 Take a pencil eraser and push the the spool valve back to reset it( the center circle when you look at the front of the gun with the barrel off)
3 Lube the barrel o-rings well with a grease type lube.
4 Put the barrel back on and slowly turn the regulator back up till the gun cycles.
The barrel assy. is pressurized when the trigger is not pulled so the gun will leak if you have the barrel off and have the tank on.
Be careful of over pressurizing the gun. Novas work at 90-100 psi
Try these steps and let us know what happens.