You're on the right track from the sounds of it. Unfortunately for you, with such a bargain basement bike, there's no set method or way to get the perfect chainline due to super lax quality control standards.
Ultimately it's going to be trial & error as you're doing right now.

Another short coming of the thruster is the crankset having a non-removable chainring. If it was removable, it would've helped to put the chainring on the inside of the spider for that 2mm you need.