Connect the humidifier with its power to the output of the controller (terminals 7 and 8, assume the current is less than 10A). Connect the dehumidifier with its power to the AL1 relay (if it draws more than 3A, you need a contactor). Set the SV to 75. Set ALM1 to 76.
Then, the humidifier will be on when R/H is lower than 74.7%, will be off when it's higher than 75.3%. The dehumidifier will be on when R/H is higher than 76.3%, will be off when it's lower than 75.7%.