Try the following. Disconnect the line going from the tank up to the fuel pump and blow to see if there is an obstruction there, especially if you are running a filter. If that works then connect it back and disconnect the line going into the carb. If that still works then your problem is in the carb. You said that you tried 3 carbs and fuel pumps so probably the problem is not there, but common mistakes are floats that are upside down or the carb filter plugged up.
Take the filter out and inspect for blockage and recheck the floats are in the correct orientation. An easy check that you can use is lightly shaking your carb after putting it together and making sure the floats rattle. If they don’t the floats are upside down. Less likely is that your lever arms are stuck closed for some reason, or your needle is stuck.
BTW, 1.5 to 2 turns on the air screw is what most people run.