You started with an inaccurate representation of Ryan Williams, since he was neither injury not confidence plague from his sophomore year in college, and you went from there. Thomas Jones, though, is actually a reasonable comparison for what Williams upside might be. He didn't have the significant single injury that Williams has dealt with, but he did come into the league in AZ, very highly regarded, was plagued with injury problems, bounced around before he got to the Bears where his career really took hold. That's pretty much the high water mark for what we might expect for Williams, if we're lucky.
I realize you've got a lot emotionally invested in none of the backs on this current roster being capable of carrying a full workload. The reality is, they each have significant question marks, and I'm not sold on any of them, either. But you've leapt to some really unsupported conclusions about Ryan Williams, and you're trying to spread it from thread to thread. He doesn't have confidence problems. He did have a very significant injury which took him a long time to overcome and put an end to the high potential he had coming out at Arizona. His pass protection has not been good enough, and he has had to work on STs because he gave nothing in that area coming out of college. That's the book on Williams. The stuff you're trying to project about his confidence or his injury history is unnecessary, and it's not accurate.
And, my personal favorite:
I've told you in other threads on this topic. You really need to do more homework on this player, because he's not what you're characterizing him to be. If he doesn't make it in the league, it's not going to be because of a confidence problem. If you haven't seen it yet, just listen to him talk. You can hear in his voice that he believes in himself and that he believes in the opportunity he's got in Dallas.
http://www.dallascowboys.com/video/2015/03/20/blitz-ryan-williams-beyond-gridiron