gas pouring out the vent hose,,,, sounds like the float/ float needle isn't metering the fuel flow to the carburetor...
i read that most Coleman's have a 2 year warranty, sounds to me like you need to save some headache, file a warranty claim, for the running issues, and the crap QC.
Or contact Coleman (which i think is manufactured by HiSun motors) and ask them if they've ever heard of the Lemon Law.