I think you got a lemon. You covered all the bases and only got it close but always had the same issue. Normally you make wholesale changes like that you go from one side to the other and then dail it in. Since nothing removed the problem i bet they f,ed it up at the factory and a replacement will run just fine put of the box with just a few turns of the idle screws.
Only thing i can think would cause fuel to be so far off is gasket sealer or gasket covering some of the ports or air bleeds undwr the carb. Other than that im betting its just a bad carb. Most carbs will at least run smoothly on most engine they are bolted to. V8 carbs will run on a chevy or a ford a small block 302 or a big block 501 caddy. They may not make big power without tuning but it will run. You can drive it without chance of fire or damage for the most part.
Hope the new carb is the trick!