The best way to stabilize your tent is to adjust the room its pulling air from. Try closing off that room except the ventilation and run a larger humidifier outside the tent, one that works on at least the square footage of the room. Get the room close to the desired range. My basement is my lung room. Temps in the basement are in the upper 60s usually between 67 and 70, and the rh of the room is in the mid 40s right now. Temps inside the tent are 70-75°f lights on and the rh is usually the same as the room outside mid 40s. If I want it higher I lower the extraction fans speed allowing the plants to transpire and raise the humidity in the tent to a reasonable level, if I struggle in the seedling stage I make a make shift humidity dome and mist the inside of it once every couple days. Otherwise I dont worry about humidity too much if the lung room is decent
After seedling stage its ok if the humidity is in the 50% range as long as temps ate in the low 70s, should provide a decent vpd
