IMO, flushing depends on the grower and the nutrient schedule the plants were/are on. I feed moderate throughout. then 2 week flush before harvest with plain water. All that matters is that the plants are healthy and u like the outcome. ^_^
Talking of building it out of wood myself. Oak to keep bugs away. once sealed. I wanted options for quality flow fans. (basically high flow but cheap cpu fans)
Your temps to not need to be higher. 79 F was my sweet spot. lowering temp during the night cycle will bring out the colors of a strain. Nothing lower that 62 F IMO.