You may want to look into the possibility of surgery and see a doctor who is up to date on modern procedures. There is a doctor in Florida called James Guerra who performs a repair using arthrex "dogbone" implants.

Treatment of grade 3 is controversial in terms of surgery vs. no surgery. Also, there are many different surgical options, some of the traditional ones providing fairly bad outcomes. For instance they involve drilling large diameter holes in bone, cutting otherwise healthy shoulder ligaments, or shortening the clavicle itself. The end result is a repaired joint that is not very strong, and this is partly why the decision to operate on a grade 3 separation is controversial....because traditional operations were ****ty.