The key to look here is that we have a divergence between the lows of 16Th and those of today. Buy call was given when we got strength in OBV (look it turns green from red) after observing this divergence. It is not a rule that the exact low of the range needs to be tested.
Yes. Can you post your full session's Renko chart for BNF today ? Just to cross-check. Here's the chart at my end using box size 8 and donchian 10. The boxed area is similar to your chart till 10am.
Nothing about likes or dislikes, it has its own share of issues. Box size big, reversal takes time also higher stop loss, if box size small it can give whips. But with your existing system if you keep it as an indicator, chances of milking trade may increase. My view only