If you can, I'd clean all the stock carb parts very well (boil them in lemon juice maybe?) and try those before the rebuilt kit. If they aren't bent/broken, you should be able to clean them. carbs can be very finicky sometimes.

to check the floats, you can use your imagination to hook up a clear hose to the carb drain (I used a grease fitting with the ball and spring taken out of it on another carb). loop that up and zip-tie it to the carb such that the open end of the hose is above the carb. that'll let you see where the fuel level is (and how the float is operating) while the bike is running.

I do wonder what would cause the gas to flow out of the vents. That is kind of worrisome. might be caused by a float that no longer likes to float, or a float valve that no longer likes to seal.

mine was doing the same think and it turned out to be a blocked jet where the main pin goes through and the diafram was mucky too kleaned it and she fired and reved up fine well after a quick cough and a pop