Id sort out the lack of water flow to begin with. Even it is OK now if you keep running it with no cooling you will be replacing the head gasket and possibly the head and lots more as well before long!
Exhaust gases will find their way out of the telltale if there is no water flow,
Where you say smoke is coming from the carb ITYWF that hose is the breather hose from the cylinder head cover. Maybe the pistons / rings have been damaged due to overheating. A compression test would be sensible
Maybe you are right and the head gasket has blown