What can I do for my "almost" torn rotator cuff? It hurts when my arm is forward and raised to about a  100 degree angle.  

Phys therapy, rest. An angry injured rotator cuff that is intact but at risk for tearing is a common complaint. We use terms like impingement or rotator cuff tendinitis to describe this. The initial treatment is recommended to be, rest from any causative activities, exercises to strengthen the rotator cuff muscles (physical therapy), a trial of non-steroidal anti-inflammatories. Injections into the are may also help.
Multiple Options. Assuming you mean you have a "structural" partial tear of your rotator cuff a well designed scapular stabilization and shoulder strengthening program without further stressing the injury may be helpful. Http://www. Theshouldercenter. Com/rotator-cuff-tear. Htm the two most common reasons patients choose surgical treatment are persistent weakness and pain (especially night pain).
Partial cuff tear. Many symptommatic partial rotator cuff tears are treated effectively with strengthening exercises. However, partial tears cannot "heal", even if symptoms improve with treatment. Many patients who are very active, or require a strong arm, do not tolerate pain with activities. Surgical repair is the most predictable way to permanently alleviate pain and restore function. Good luck!
Cuff tear. Depends on your age and activity level. For high grade partial tears, most active individuals will do better with surgical repair. This can be done miminally invasive through arthroscopy. Other options would include rest, physical therapy, and injections.