Proven, how? Has DBP ever provided, even once, a call involving a market fill? A stop loss and target?
If you learn to read a chart from left to right, you can use any chart to prove to yourself that this system works. Its almost easy, and its right there, in plain sight. If you just follow the rules of drawing the supply lines and demand lines, entering on the retracements, and exiting on breaks, you don't need anything else.
As for fills, sure, this is hard to figure out, but you will notice if you study enough that he has said many times that he doubts certain trades would be filled. And lets not forget, the trade is entered in the retracement, where the activity has slowed down, not in the initial breakout phase that of course would have trouble getting filled.
You don't need targets because we aren't trading mathematics here, we are trading the behavior of other traders. You stay in a trade as long as the trend continues and you exist when it changes.
Making target calls, although he does very well with AMT, is tricky because you ultimately never know what will happen. If nobody wants to buy something that showed good promise, then clearly you shouldn't buy either, and price will tell you this, so even if you went long, you get out right away. A good trader can change his mind in a split second based on what he sees. Saying that price will absolutely reach a level is looking for absolutes that just don't exist in trading.