He didn't say "cheat day" he said cheat, which I take to mean a cheat meal. There is nothing wrong with that. If you have at least a 1000 calorie deficit each day, one meal isn't going to change much at the end of the week. We all know that being on a diet for a long time kills your metabolism and the occasional cheat is just the thing you need to juice it up.
As for the OP, I think the solution to your problem is pretty easy. Forget almost everything you know about dieting and start over. I've done that a couple times and continue to make progress. There are quite a few different avenues you can go down in trying to get cut. Carb-cycling is a good one, for example. I know it can be frustrating, especially when you think you should know it all (as a PT).
Bottomline- you need to mix it up now and then to keep your body guessing.
I do agree you may be over doing it on the cardio. You really shouldn't need to do that much to lose fat. I went through the same motions about a year ago. I would do over 1 hr a day every day of the week. Some weeks I would lose a pound, others I would gain. My diet was pretty consistent, with minimal cheating. Now that I'm a little smarter I can do 20-30 minutes a day 3-4 days a week and get better results. My diet is still fairly consistent. My training has increased, so that may have something to do with it.
You should read any/all articles by Chris Shugart on here. He is king of leanness and I pretty much take anything he says for gospel. Go to his Blog and read the latest article "Out of Balance". This may specifically help you right now. Again, everything he writes is with leanness is mind. Not to sound weird or gay, but he's my personal Jesus.