It's all new. As long as fuel isn't getting in. It doesn't leak. Yes I checked everything possible. So what you saying is when you buy a new carb, expect to buy new parts to fix the new carb. That doesn't make sense.
It sounds like it is overflowing instead of leaking. I would think it has to be something with the needle or float. Since you have adjusted the float already I would look to the needle valve. Could possibly be the float taking on fuel affecting its buoyancy.