Hi there,
I agree with Ian that your little guy look very thin, and the temp is a bit to high. With regards to feeding he/she looks a little younger than my brood of 10..plus one that lost his tail( lost count of how many weeks old they are!they may be around 12 odd weeks old) The rear legs don't yet look fully developed. I currently feed mine on small cut up live earthworms and they are growing at an amazing rate. Prior to this it was live brine shrimp( well rinsed of salt) , daphnia and blood worm..these all need to be alive and not dried or frozen. Most fish/ pet shops will stock this..and the earthworms you could use out of the garden as long as its chemical free. If he was with his siblings he may have not had as much access to food, but now he has you he'll no doubt start feeding and putting on weight..mine are still fed twice a day and any access removed with a turky baster.
The tank needs to be cooler and approx 20 degrees or below, I personally use a fan that blows across the top of the tank, having said this we are now cooling down as it is autumn here so i don't need to use the fan. I have seen clip on 'reef' fans that are reasonably priced on e bay that seem to work very well. The alternative is to keep the windows and doors closed and covered to keep the temp/ sun out.
If your tank was not cycled you need to do daily 20-30% water changes till the reading for ammonia, nitrate and nitrite have dropped , you will need to get the water tested iether at a pet shop or buy individual test kits. I do mine at home and record the readings in a booklet, this was mainly a type of diary for the kids but now they have lost interest its now for my use.
Hope this helps a little..keep us posted on how little Kirby is doing.