The UTH is 12" x 6"? That's not tiny...it's huge! You want one that covers only about 1/3 of the tank and you only have a tiny tank, don't you? When you say it reads 85, how long after you turned it on did you take the reading? They can take the whole day to reach their maximum temperature. The purpose of regulating the temps isn't because of fluctuation; it's because it might go too high. Make sure to check the temp again after letting the UTH be plugged in at least a day.
You should feed in a separate container, but just don't place that separate container on any heat source. The feeding container is too small to allow him to escape the heat if he's too hot. Your feeding container doesn't have all that stuff in it, does it? It should be completely empty and bare when you feed him. Since he has probably regurged his meal, you will have to wait at least 8 days to try again.