jetting affects the amount of fuel metered into the engine while there is air flowing through the venturi. the carb leaking after sitting has nada to do with jetting, either the float is stuck or the float needle isnt sealing. that could also happen from leaving your petcock on after parking the bike..tap the bowl with a screwdriver handle and see if the leak stopps.
when you say mid range is slow what exactly do you mean? this is a mostly stock moped.... is the bike running smoothly in the mid range? breaking up? you should hear a smooth increase in rpm, no choppyness.
i think your on the right track. im not sure but 72 seems rich to me.