Mold - Please Help

My son lives in a rental house in Northern Calif. He and roommates are young and don't use the heater ever/no air conditioner. Single paned windows that condensate and have mild mildew around them. His bedroom has a mildew smell, he found a handful of clothing items like thick sweatshirts in closet with mold and threw them away, the rest in the closet no signs us smells horribly with mildew smell! The window itself is NOT leaking, i checked by pulling the carpet up near it, no sign of water BUT the entire room is moist 68% humidity on a digital gauge. The carpets are moist, his book pages are moist. Under his bed we found a molded backpack everything else was not molded yet under the bed. We dusted the entire room and vacuumed and cleaned the mildew from the window and shower master bath. We came in and cleaned the mildew off the window, he does have a master bathroom, normal amount of mildew in the shower that we also cleaned. The fan in the bathroom is okay but we bought a super strong one that we can install this weekend. We are NOW running a small fan and a small Homedics hemp air filtration which lowered the humidity only to 63% . Should he start the heater? they never have used it ever, would it dry things out or just spread spores? We are ordering a de-humidifier and we heard of Theives essential oil diffuser that is guaranteed to kill spores. I get very itchy throat and skin when i went into his room, but my son has no symptoms so far and he lives there and sleeps right in it all. Do we really need to through away all porus items if they don't have mold but still smell mildewy???? Is there a way to remove the smell from these items once we get things under control? We did go under house and we had tremendous rains this year and no standing water but damp soil. Haven't gone into attic yet. Is it possible that the single pane mildewed window near the master bath that those two itself caused the high humidity???? or do we need to figure out a deeper scenario. The room is moist, i can feel it when walking on the carpet and touching books and boxes. HELP