VPD and ventilation flowering and spider mites oh my

Hey guys what do u recommend for vpd and ventilation and c02 setup. Newer grower here. Actually my first grow went really late in veg (3 months) my question here is how do u recommend setting up a sealed room I have mine with an exhaust that doesn’t run during the daytime and is on a sensor at night for humidity . C02 tank is on at day time and off at night (actually 1 hour before night to save some c02). So how do u guys run your sealed room for proper VPD because I have a hard time keeping my humidity below 60-65% and temps are high at like 26-28 usually on the higher end. I also don’t have a c02 sensor I just keep it at 0.5 on the regulator. I’m wondering if there is a good humidity and and temperature I can follow without getting bud rot somehow With what I’m working with and what do u guys do for ventilation all while battling spider mites too. Mid flower. Just got predators