I am having the same foaming problem with the same mini regulator using a picnic tap. What did you do with your lines and all?
Also it uses up the CO2 (78g) too quick. I tested and hooked it up with a brand new keg and new cartridge, set it to 4 psi and left it alone. Next day, the co2 was gone. I didnt even pour any beer from it. My keg doesnt leak, so Im not sure whats going on. I know the regulators have a release to release keg pressure as you turn down the regulator.