As a general rule the respiration rate is increased as the temperature increases. Photosynthesis is not as closely tied to temperature as is respiration but there is more photosynthesis at higher temperature so the recommendation for a cooler temperature at night than during the day. Carbohydrates are made during the warm days but are conserved at night by lowering the temperature thus reducing the respiration rate. I'm not sure of why the increases that were selected are the ones to use. The logic is that on cloudy days there will be less photosynthesis than on sunny days so the cloudy day does not have to be as warm as the sunny day.
Photosynthesis is slowed down when a lot of end product builds up in the plant.
That is if sugars build up from photosynthesis, the photosynthetic rate will be reduced. There is some good evidence that photosynthesis will occur more rapidly than the carbohydrates can be translocated to other parts of the plant. That means that translocation will continue to occur after photosynthesis has stopped because the sun has set. During the early part of the night, translocation will continue. Certainly by morning everything has been moved so the plant is ready to photosynthize for another day.