My Implants Have Dropped and Separated. Is This my Surgeon's Fault?

Unfortunately, in your situation, it is hard to know exactly why your results did not turn out the way you had anticipated.  Without seeing your pre-and post op photos, knowing what went on during surgery, etc., it is impossible to tell.  Sometimes the muscle pulls the implants over to the sides more.  Sometimes the implants cannot get any closer because this is exactly where the muscle stops, and to weaken it would cause the potential for symmastia.  The implants might be too narrow, or your own breast tissue may be pulling too much.  There are so many variables, that it is impossible to know whether it was from something done during surgery or just the way your body want to heal.  With regards to cost, each surgeon has there own revision policy, and should be clear up front what those costs could be.

Without an examination I can not say. but you are out long enough that you will probably see no more improvement. It can be you have capsular contracture, which moved the implants, you can have implants that are too small for your diameter of your breasts, the pockets could need to be modified. There are many possibilities, but without an good examination it is hard to tell.
If uncomfortable with what you are being told, get a second opinion from another board certified plastic surgeon.