The study claims that the output from a CE4 is dangerous at any power level. I associate PT coils similar to a CE5, which I don't know if they are actually any better than a CE4. I really have no experience with those devices.
The heat flux on a 2 ohm 33g wire coil is 330 at 6.5W, you must find the vape quite hot. They recommend that you try and keep the heat flux in the blue when rebuilding clearomizer heads.
Here is your current build in Steam Engine.