What average global temperature is maintained when there is a balance in earth’s energy budget?

The incoming and outgoing energy at the Earth’s surface must balance. Or in other words,  the flow of energy into the atmosphere must be balanced by an equal flow of energy out of the atmosphere and back to space.
Earth's Energy balance describes how the incoming energy from the sun is used and returned to space. All of the energy entering earth’s atmosphere comes from the sun. Half of it is absorbed by the earth’s surface i.e. the land and oceans, 30% is directly reflected back to space by clouds and 20% is absorbed by the atmosphere and clouds.Earth's actual average global temperature is around 14° C (57 F).

Yes, endothermic means it turns cold. and some chemical changes include change of tempature.