1966 Plymouth Valiant /6 & Holley 1945 carb can only get to idle at 1250rpm. How to get a lower idle without dying?

I don't have to two foot it anymore. Took it for a test drive and it sputters/wants to die if I give it more than 50% throttle. If I mash the pedal, the engine cuts out completely. I'm thinking either a clogged jet or a leaking gasket. I'm gonna spray around the carb with some carb cleaner, and if I don't get anything, then I'll take it apart and clean it. When I took it out of the box, I could hear what sounded like a ball bearing bouncing around. That normal?

EDIT: the sputtering has gotten better. Happens a little less often and a little less frequently. Most noticeable when accelerating onto freeway speeds of 65mph.