I'd just get it as high as possible to try to try and minimize the heat. With your outside temps the chicks can be fully weaned off heat next week at the latest, unless temperatures drop dramatically.
Raising it is the way to wean them off heat but it's either not functioning correctly (overheating) or your brooder is located somewhere warm (or poorly ventilated/trapping heat), so the ambient temperature inside the brooder is high too.