Ron had to give them something NEW for him to get the deal. And if Ron was sitting on info for a year and half, to me that only means he was involved, otherwise there is no need for him to not tell LE everything he knows from the get-go.
I don't think it is simply Ron agreeing to testify, because he would HAVE to testify if the prosecution called him to the stand in any case, drugs or in any future murder trial.
The only reason Ron could legally get out of testifying would be if he plead the 5th and didn't want to incriminate himself in anything...
So they are not going to give him a deal for simply testifying, because he would have to testify. It has to be more than that. He had to give them something NEW.
I agree with you. But I don't necessarily think it was something "new" that Ron gave them. IMO, they wanted Ron's story to compare with the evidence they have to get Ron. Ron gave a statement under oath without knowing what evidence they do have. That will keep Ron from being able to change his story or tailor his defense to the evidence.
IMO, the fact that they sentenced Ron prior to any testimony says that they are going after Ron. They no longer have anything to hold over Ron to get him to abide by the plea agreement. So all I can think of is they wanted his statement on record knowing that they were never going to need his testimony.