Just my opinion, but I think proper alignment is more important. In a self defense situation you may not be able to see your sights. If you can consistently grip your gun such that the barrel lines up with your forearm, you can better align your gun on target without sights. Even if you are able to use the sights, you'll be able to get them on target quicker if the gun is aligned properly.
Trigger finger placement is less important than being able to pull the trigger straight back. On my DA semi-autos I use the pad of my trigger finger and have no problem pulling the trigger straight back. I also have small hands, and I can shoot my Beretta 92FS, with it's big grip and long trigger reach, pretty well.
If your shots are going down, the problem isn't alignment, it's trigger control. I would suggest you work on trigger control with dry fire practice. Hand strengthening exercises can help, too.
This video may be helpful:
But probably the most helpful thing would be to get with an instructor who can see what you're doing and help you improve.