Hi Dichotomy,
It's great that you're looking for constructive help. I'll throw a little caution in here, first thing. You may get too many suggestions, in the spirit of folks being helpful, that may not be appropriate for you at this stage of your development as a player-pilot.
The 51 pilot you were up against is experienced and good. He flies the 51 often. You can discern from his score that he's aggressive.
Before going too deeply into all the facets of SA, and there are many, there are some more basic things you could work on to build a good foundation. One is making sure you have the "look forward" view mapped and set up. You'll find a write up on setting it up in the trainers link in my, or Murdr's signature. It will help you in your gunnery, along with what Murdr has suggested.
Set that view, then set a target in the training (or main) arena and practice rolling into shots with ailerons. Target command is .target 400 where 400 is distance in yards. You can set any distance and close the target by setting distance to 0. The target will always be north.
There is little energy cost to gaining a guns solution by using ailerons. Your E losses come from pulling g's with elevators and rudder deflection. So, practice shots from different angles and attitudes. Roll your airplane into all kinds of positons and practice firing from inverted angles. It's fun to do! Make a game out of it, like throwing hoops. Watch your tracers drop to earth, even if earth is "up" from the cockpit. We can't always be perfectly in plane and upright for every shot.
Experiment with rudder input and power settings. Get used to adding some right rudder as you add power, even while you're firing. Only by practicing and doing it, will it become second nature to you. It will become automatic after a while.
Good rudder work is important, not just for maneuvering and energy management, but for gunnery also. Good rudder work will accelerate roll and help you get the nose of your plane flying smartly toward a place where you anticipate your opponent will be, not where he is now.
Hop into the training arena and get some time with a trainer. Get those fundamentals down and you'll develop faster. !