Wife at her wits end - Toddler hitting, not listening. Need advice

Hello all,Over the past couple of weeks our boy, 2 years old (25.5 months) has started hitting and headbutting when he does not get his way/is asked to do something he does not want to do.Then randomly he is like Dr. Jekyl and Mr. Hyde - Super loving and affectionate, then slap across the face. Asking for a hug, then headbut to your eyebrow.We started potty training on Friday, and his bad behavior has only amplified...to the point that my wife is on the verge of throwing in the towel on potty training.Our son knows a few words. He comprehends instruction very well and is capable of completing simple tasks such as helping clean something, throw things away, help put his toys away, etc.We are pretty firm on the notion of not hitting/spanking our son, and are looking for other forms of discipline that are effective with a strong willed child.Time out? lol please. He does not mind it at allMy wife said that she had a mental breakdown today after/during our son's little kids gym class as he did not listen and she had to leave early due to his bad behavior (hitting other kids, taking their passies/water cups, hitting my wife, overall not listening to her or the class instructor). She says that she feels like a bad mom and is done with "this parenting lifestyle."Any pearls of wisdom regarding our son's behavior you can drop would be appreciated. Anything to help encourage my wife would be a help too.Thanks in advance for your time. via /r/Parenting http://ift.tt/2sdFFy9