Rocket, I'd say to go with that slide. Unless this college coach is from one of the big bowling schools, I would say go with the coach who's been teaching him. Also the slide will allow him to do a lot more and save his joints so much. Anytime I hear somebody say they thinking about not having a slide I direct them to Tommy Jones how is a high rev and speed player that has a such a smooth slide and is on balance that it allows him to have a smooth release and get all those revs and speed. As for the shoulders, it's Jordan trying to get his body lower. Easily solved with a getting low with his legs.
Yeah the left arm is the arm that righties are supposed to bowl with according to Norm Duke. It's the O-line of bowling. Makes the right arm look good but bares all the weight of the ball and does all the work in relieving tension in the right arm. After it leaves the ball it should travel to be parallel with his slide leg for about a step, then out in front of him as the slide approaches and then whip it to the side for its finishing position.
Be like water making its way through cracks. Don't be assertive, but adjust to the object, and you shall find a way around or through it. If nothing within you stays rigid, outward things will disclose themselves.