ChrisConley,
You are correct if I understand what you the question is.
The energy conversion of 2545 BTU/HP is for useful work done by the motor. For example, if the motor drove a pump, the motor is doing useful work driving the impeller pumping a liquid to a higher pressure; this developes heat. The heat in this example is normally dispersed through the normal flow of the liquid; only if the pump is deadheaded (no flow) is a lot of heat generated that can damage the pump.
In your case, useful work is being done to forcefully flow air in a duct which will impart heat to the air flowing in the duct - but again that is normally dispersed without a significant increase in air temperature due to the large amount of air flowing and the fact that fresh air is probably being drawn in at 20 to 100% of the total air flow.
There is no useful conversion of energy between the air in the room and the motor. You only need to determine what the normal motor surface temperature is for full load amps; and then calculate the heat released to the atmosphere via radiation and conduction. It will not be anything near the complete energy conversion of 2545 BTU/Hp for the motor.
The more you learn, the less you are certain of.