You might have to take baby steps with opening your shoulders on the backswing. Before you start your approach open your shoulders a little where your ball side shoulder is a little behind your balance shoulder and you add your lateral spine tilt to the side with your ball.
Also throw in a little forward tilt. As you swing back your forward tilt will increase some. When it does keep it there through your release.
With that lateral tilt to your ball side the swing will remain under your head on the way back and forward to the release. When you get use to opening your shoulders a little on the way back you can open them a little more as your confidence builds. You don't necessarily
have to have them open so they are parallel to the lane you are bowling on but open them as far as is comfortable to you. As long as you open them some your ball speed might increase some. With the technology in bowling balls now with the different cores in them a higher speed if possible will make your ball work the way it should. Depending on the ball you have a too slow speed will make it hook too early especially if you play an outside line on a Typical House Shot pattern which is used mostly on regular house leagues.