Hard to understand exactly what you're describing here...
It dies ONLY when at idle? But otherwise it'll run down the road with your foot into the pedal just fine? This tells me you do NOT have fuel starvation issue of any type, in advance of the carb itself. Adding another filter in-line is senseless in my opinion. One is all an engine needs...and even that's only needed if/when the fuel supply is dirty...
So if you indeed have a fuel problem, it's within the carb's idle circuit. Or possibly vapor lock. Easy to exclude vapor lock by wrapping that pump-to-carb line in tinfoil and see if it cures the problem. You could also have your fuel delivery blinders on and your problem may have nothing to do with fuel delivery...could be any number of ignition problems, could be vacuum prob, could be valvetrain issue, could be imbalanced compression, mostly SOUNDS like an air leak...but like everyone else, I'm flat out guessing...
What's the state of this carb you "threw together" and installed? You say it's a "clone", what does that mean? How did you establish idle mixture settings with that carb? How about accelerator pump settings? Float level? What's your idle speed set at? Base ignition timing? Could it be actually FLOODING itself dead? Or are you certain it's actually leaning itself dead of fuel starvation? When it dies and doesn't restart have you immediately checked for spark? Or pumped the throttle while looking down the throat to confirm whether or not there is gas in the float bowl? When it's colder and running good, does it have a bog when you tromp the throttle, or do you get instant power?
Frankly IMO there are way too many variables here to effectively internet troubleshoot. Grab yourself a good trouble-shooting guide (factory service manual, even chiltons or similar guides will be adequate), follow ALL your symptoms, and check EVERYTHING the guide tells you to check, IN THE CORRECT ORDER...skip NOTHING, rearrange NOTHING, and assume NOTHING. Brand new parts are sometimes bad out of the box, rebuilt carbs are often improperly set up, under-torqued/leaking at base, etc...
Ethanol...there are books and websites about this topic alone. Suffice it to say for your purposes, assuming you're running the typical 10%, it's a leaner burning fuel than pure gasoline. Usually results in the need to enrichen mixture from factory settings a tiny bit to compensate and get a good burn. But if you don't have a factory carb, you don't have a baseline setting to start with anyway. O2 sensor and a/f gauge is really the best way to tune fuel mixture on any gasoline motor. Otherwise you're stuck with the inexact science of plug reading...which by the way could give you HUGE clues if you read the plugs. This will tell you at least if it's dying due to a rich or lean condition...what do they look like?
