The "positive expectancy" is irrelevant. Unless and until you test your hypotheses thoroughly, backward and forward, then determine whether or not the plan is consistently profitable, you'll never be able to trust it, and if you can't trust it, you'll never be able to find the discipline to trade it, and absent all that, you'll never be able to trade size.
What would you recommend doing to test it correctly. I've done live market sim and also studied previous session charts.
You can start with this: Developing a Plan. Once you have the overview, the following threads may be of help: Observation Backtesting