The putting grip should be in the lifeline of the hands, not the fingers, so that you eliminate your wrists and hands from the stroke and allow your putting power to come from your shoulders
When faced with a bad bunker lie you need to close the clubface slightly so that you can dig into the bunker and get under the ball but most importantly don't try to do too much with the shot, all these shots will come out with over spin and release so you need to play to the fat part of the green
Use this shadow drill to get your weight behind the ball and hit higher shots