I'm no carburetor expert, but here's my thoughts. With no visible fuel squirt when you hit the accelerator, that means your accelerator pump is not working properly. Running with the choke partially closed will give you more fuel, so the accelerator pump issue will not be noticeable - you're covering up the lack of an accelerator pump squirt by introducing more fuel into the system with the choke. So, we need to determine why your accelerator pump is not squirting.

On my Holley, when you hit the accelerator, the accelerator pump cam pushes on a lever, which then pushes on the accelerator pump diaphram, which forces fuel through a passage and out of the squirter. A spring inside the accelerator pump bowl forces the diaphram back when the accelerator goes back to idle position. If the lever is sticking, the diaphram will not return, and the accelerator pump cam can move all it wants but it won't be moving the lever (since it's stuck), and you won't get a squirt. The same thing would probably happen if the spring behind the diaphram was broken - it wouldn't return the diaphram, and you would get no squirt. You may also have a plugged passage to the squirter, or a plugged squirter, or even a wiped lobe on the accelerator pump cam.

The way your carb creates the squirt may be different, but the principles should be the same - something pushes on the diaphram, causing fuel to flow through and out of the squirter. If the diaphram isn't being pushed, or it isn't returning, or the system is plugged, you won't get a squirt.