[Home Defense Gun]

Try using what Massad Ayoob calls the Power Stance - basically the isosceles with the firing side foot a bit back. I learned the isosceles but found myself always dropping the foot back in stress situations. You should be in a slight crouch, shoulders hunched forward. Do a search on Power Stance, there is a lot to it.

I second what everyone else has said about front sight focus and grip. Keep at it.