RE: Shoulder Pain?
To put it in terms you'd understand, you do not have someone who's never lifted starting out with 300 pounds on the clean and jerk. They're almost certain to get injured because they don't have the proper form. No matter how strong they are, you start them off light and let them work up as they get the proper form ingrained in their lift.
Same thing with bows. You don't start a newbie off with heavy draw weight and aggressive draw cycle on a cam with an almost non-existent valley - which describes most cam systems out there today. Whoever sold you the bow should be hung by the gonads with his own bowstring.
When your shoulder heals, do like the others have recommended: back the bow off to 60 pounds and start there. Then you can slowly work your way up to 70 as you get the proper form established.