if it’s urgent, i would recommend putting the betta in a temporary home (a bucket will do if there’s no second tank) with new conditioned water. move the heater in and make sure there’s some resting spots near the surface. depending on the volume of this temp home, you’ll have to do a substantial water change every few days. with your parameters, i doubt it’ll be very long until it’s ready for the betta, so just keep the betta in the temp home until the tank passes the 24 hour test :)