Hello Jimmery,
Here is a link to the X block PDF, as to the stat, it is a simple make/break type stat.

http://www.blueridgecompany.com/documents/X-Pump-Block.pdf

As to the forced air, if this is on the domestic hot water side you would use a bronze or stainless pump with switch relay built in or a single zone relay you will be fine. If the air handler is placed above the water heater convection and the short distance of run to the unit should prevent water from stagnating in the unit.
The forced air heat temp will be the temperature of water in the water heater.
Dan