You can feed her every 5 days an amount equal to 10%-15% of her body wait. Just make sure the feeder item isn't any bigger in diameter than the largest part of her body. Once she hits about 600 to 700 gms you can cut her back to once a week.
The thermostat probe should be positioned over the hot spot as should the thermometer probe. If you want to make sure it stays securly in place you can hot glue it down in the tank. If you are using a rack system, position the thermostat probe so the tub will not dislodge it when sliding in and out. The thermometer probe should still be over the hotspot inside the tub.