…then I get the open of the previous (old) candle…
As of this version of PRT and before the new MTF one is available what you call OLD candle is indeed the CURRENT closed candle, since ALL strategies are executed when a candle closes, just before the next one opens (actually, since it may take some microseconds, the new candle is likely to be already opened when a strategy is still being processed, but cannot be accessed until it closes).