Your naturally arms curve inwards, so you need to place the club in your left hand using this angle so that your clubface can return to impact square
The better you practice on the range and the more organized you practice session is, the simpler the game of golf will be out on the golf course
Your posture is determined by your arm swing. If you swing up and down on a two plane swing then you should stand more upright. If you swing your arms around on a one plane swing then stand more bent over on the balls of your feet.