Sounds like a lean fuel mixture problem. Possible air leak in the rubber boot between the carb and cylinder, or the carb is still not clean.
I am leaning towards this due to the improvement in starting after the second cleaning. If you squirt carb cleaner in EVERY hole, you should get carb cleaner exiting somewhere else.
The amount of throttle opening and rpm suggest a problem in the main needle (not float needle) and its associate components as the most likely area. Or........are you sure the float boal is filling with fuel and the float level is set correctly? That would also give you fuel starvation symptoms.
Another recent carb problem post dealt with a new clark tank, new petcock and fuel delivery issues also. May be some common issue there as well.