Tensioner on water pump?

The tensioner on the water pump drive belt could be a problem but it wouldn't make much difference in the engine smoking, stalling, idling poorly unless the engine has overheated and blown it's head gaskets due to the water pump drive belt being loose. That would explain the smoking and everything else that you experience. I think you need to find a Mazda specialist for a diagnosis and estimate. If you want to find a specialist, here's a directory l;ink for you: https://repairpal.com/mazda-repair-in-flemington-new-jersey