There are a few reasons why to use historic ATR. One is, more often then that there appears to be an inverse relationship between the OR and the range the rest of the day. I've talked about it frequently on this thread that when OR are very wide, the rest of the day usually is choppy. When OR is narrow and tight, the rest of the day is volatile and trending. Now this is not always the case but more often then not it is. The 5 day ATR is trying to capture the vol environment we are in. It dynamically adjusts to changes in vol over time. Also the OR dynamically adjusts to volatility.
Time stops are very important. I don't just use time stops for A level violations and neither did Mark. If you get long anything there is some assumption it should start working at some point. If it doesn't, you probably want to get out. Now there is a difference using time stops on say a failed A down vs buying a confirmed A up. On a failed A down, your time stop should be strictly enforced even if the A level is not violated. The reason for this is, if you get long at the lows and the market is sitting there, it's going lower, that's trading 101. Now if you get long near the highs and the market is sitting there, it's probably flagging and will break higher.