I came to that realization months ago, Suspicious, when Shoemaker started talking about a deal for Ron. We knew they didn't need his testimony against Misty to nail her on the drug charges. If Ron was holding a trump, it had Haleigh's little face on it.
No one will ever convince me that Ron wasn't lying during the 911 call. He might not have hurt Haleigh, himself, but he knew damn well who did. Or thought that he knew, and had reason to hide what he believed at the time to be the truth. Personally, I believe Misty killed Haleigh and somehow convinced Ron that he was responsible. There are other possibilities, like an act of vengeance for one of his past dirty deeds. The point is that he and/or TN made a hasty decision that night, and once the cover-up began there was no turning back. He wouldn't go to LE later and say, "I thought I was responsible for my daughter's death, so I lied about it. But I found out that it wasn't my fault after all. So now I wanna talk." Not unless his life depended on it. No matter what Lt. Greenwood said, it was no accident that Ron got involved in the drug operation. When LE set up the sting, they knew exactly how it would play out.
The fact is, he still might not know exactly what happened, but he holds enough of the missing pieces to make his testimony valuable. For instance, in the beginning he stated that the bed had not been slept in that night, even though Misty claimed she had been asleep since 10:00 p.m. Misty stated that she washed a blanket. Ron said there was no laundry detergent. Those are just a couple of small details that we know about which could potentially be part of Ron's testimony against Misty. It's not enough to win a deal, though. There has to be more. Unless, something really is rotten in Putnam County.