You claimed that EPA combined has a towing element to it. Please cite the EPA documents supporting the claim.
You also claimed something about towing and 40%, still waiting for a published cite to support that claim.
Research? I'm a powertrain engineer working in a building of several hundred thousand square feet that has something like 50 or 60 dynomometers running 24/7/365, with an oval test track couple hundred yards behind the facility. I can tell you that towing fuel economy is given like zero attention. There are way too many variables to run any kind of application testing. We do however extensively test product capability while towing.