I'm quite confused about Willie. He started out as a "bad" guy. We can't be sure how violent he might have been, but he clearly had a hot temper and easily got into fights. Then Barnabas bit him and mistreated him, and he became quite changed. However, he was under Barnabas' power and, at least in the beginning, was beaten by him. He then tries to warn Maggie and gets shot numerous times and is left as the scapegoat by Barnabas.
At that point he becomes insane and forgets who Barnabas is, etc.
So, now he's recovered, or mostly. He recognizes Barnabas. One might think that he had forgotten a lot, but when Barnabas points out that it was during the day that they saw him at Windcliff, he immediately realizes the significance of it. And the first thing he does is go to Maggie to try to explain what happened. It would appear that he does remember the prior situation, or at least most of it.
Yet, he seemed very happy to see Barnabas at Windcliff - remembered working for him and was anxious to return to that life. And, that's before he knows of the "cure." Initially, I figured that he had really forgotten his previous life and just assumed it was good. The later developments would indicate that he DOES remember, but then how could he have such "fond" recollections of it?!!!