To me, a 4hr for trend seems way to long for 15mn expiry. Try 30mn for longer trend and a 5 or 10min for short term, might reduce draw down. Can't help u with mt4/5 script. I do a lot of scripting in think or swim, when i look at script in mt i just shudder. in ToS u can set up a constant scan of a watch list of ur assets and set the time frame for different indicators, i.e. 30mn for trend, and the lower time frames for trend/sar. then make pop up alerts with text. u would have to have the alert on each chart. if u want, we can share ideas(could send u some screen shots), firstname.lastname@example.org. but mt script ur on ur own. i also like zigzag for trend and waves, have %retrace at .00618, u won't see a move of 5% in the currency markets.
IT seems that you are doing well basing on "trend-following". So the problem is the SL, maybe you put SL to tight so it's easy to get hit. Please let the price "some room to breath". You also can do back-test when you are free.
About your system, you say that you use Parabolic Sar (Para), so I get an idea:
1. Direction: you should look at D1 for direction, for example Para says it is in up-trend.
2. Signal: you can use H4 or H1 depending on your time with trading. Here for instance we use H1. If Para in H1 time frame is in up signal, we not enter, we should wait for the down signal, and then the up-signal again => then you enter for LONG (you know what i mean, right? ).
By doing this, maybe we will miss some pips, but who knows the market will go... By doing this, we will prevent buy from the high price, and maybe market will turn back and hit our SL. By doing this, we can buy the lower price.
3. Stoploss: you may put it at them highs and lows in H1 (theory), or you can use 50% of ATR Daily (ATR indicator). For example, ATR of GU D1 is about 90-100; if today ATR Daily is 90, I will put the SL about 50 pips.
4. Money management: You can risk 3%, 5% or even more at your choice. For example, the capital is 1,000 usd, you are "HAPPY TO LOSE" 5% which is 50 usd. So with SL of 50 pips, the lot-size should is lower than 0.1.
Hope this helps a bit ^_^.