If that was an offhand group, then you are definitely getting the hang of it. Don't try to approach the target from any particular direction. Establish NPA on your frame, and hold on your sight picture and allow your brain to do the rest. You may find that you need a particular windage adjustment for your standing slowfire that is different from your other positions. This is not uncommon because of head placement, recoil effects without the sling, or particular behavior of the rifle. If you just allow the hammer to fall while looking at the front sight, you will know where it was. In a match, take your sighters from standing, and dry fire in prep. Trust your call. If it looked good but came up left, be bold and make a sight change. As for a doubling Garand, I had one too. It can be a real PITA. If it is prone to doubling with correct trigger control, you need to establish a bit more second stage movement. Because of recoil, these rifles need a small bit of second stage movement (creep) to prevent doubling. In a good trigger job, it is smooth and almost imperceptible, but can be seen. Getting a Garand trigger down to 4.5 pounds often reduces sear engagement to the point that it will double. It will make you alter your trigger control to prevent it, and cost you points. Just a touch of creep will fix it.
It is easy to do with a piece of 400 grit emery cloth.