The only problems that might occur would be a) if the fridge tends to vibrate it may stress the T. Then again, it may not. I'm not sure how T's would handle consistent minor vibration. It would be something for him to observe though. The T may acclimate to it's surroundings just fine with it.
And b) just the fact that the enclosure is high up increases the risk of an accident. (dropping the tank etc.)
I don't think the risks are too horrible. As long as he was aware of what they are. Again, that way he can be more observant of the T and the effects of it's environment on it.
Oh, 75 degrees is not really too low but a couple or so degrees warmer in the day wouldn't be a bad idea.
Hope that helps some.