You need to use NT8, not NT7. I used NT7 5 minute bars and they give incorrect back testing results because the back testing software execute the code per bar.
In NT8, Strategy Analyzer there is an option for Fill Resolution. Choose 1 minute, so you get better resolution in your back testing and then back testing on 5 minute bar and see if you see a difference. Every 1 minute, your code will execute. Also, you can use tick replay, every tick your code will execute, I think. I do not use NT anymore. I am going off memory.
Also, check about 20 trades and see if it make sense to you.
Your results look an error somewhere.