I try to get the arch of my right had as far up on the grip as possible, so my trigger finger seems to slant down over the trigger a bit. The middle of my trigger finger does touch the frame between the first and second knuckle.
If I hold the gun in my right hand and squeeze the grip like I would when I shoot, the gun moves to the left a bit. I can feel my finger pressing on the frame above the trigger. Hmm... Interesting... Seems **** gripping more firmly with my support hand and making sure my trigger finger does not touch the frame would be two good things to do.
If your finger touches the frame, the gun will move when you pull the trigger. Try rotating your hand so that knuckle moves slightly forward. You can help this along by using the "?" tip by putting the center of the trigger more toward the tip of the finger. Don't go too far though.
It also seems to indicate to me that you need a shorter length of pull or become a master at some weird Hindu body stretching art.
Additionally, verify that you are pulling straight back and not at an angle. I suspect the combination of a short finger/long LOP is causing you to pull back and left.
You can offset this movement by exerting extra pressure with the support hand and/or pressing *slightly* with the thumb on the side of the frame. You'll have to figure out what "balanced pressure" means to you. However, I do recommend that you not do the latter trick unless absolutely necessary. The only way to mitigate this when shooting with one hand is to tighten your grip and use the "?" trick.
I noticed that you're using a Glock 19 and a SIG P250. First off, dump the P250 and get another Glock 19 or 26. The reset on that P250 is terrible because it's like a revolver: it forces you to return the trigger fully forward for each shot. ICK! The Glock, on the other hand, has a very short reset similar to that of the 1911.
You should shoot "off the reset". This means your first shot in a sequence requires you to pull the trigger starting from the forward position. After the first shot, you will feel a click as you bring the trigger forward. This is the Glock reset engaging. The gun is now ready to fire, so don't release the trigger. Releasing the trigger results in wasted work and slows down your shooting. Pull from this shortened position for all subsequent shots. I recommend that you try this in dry practice first.
You may find that the Glock is still too long for you. In that case, look around for other guns that have shorter LOPs. I would suggest you look at the Springfield EMP, Browning Hi-Power, 1911 with short trigger (and possibly thin grip panels), and similar handguns.
Finally, take a notebook and ruler with you to the range. Document your grip, stance, target and results. I found this very helpful for developing consistency over a series of range sessions.