My son just turned 19 years old and has become very disrespectful…

We've sat down and did all the above exactly the way you've stated it. But he continues to disobey the rules and she continues to tolerate it. For instance, whenever I confront him about something he’s repeatedly done wrong after stating the rules over and over again and giving him very gentle and polite warnings of the consequences. “Jo, you know what I said about not cleaning the bathroom up.” Then I come with a strong commanding voice ----sort of military strong but low in tone and using some body language because I’m much larger than he is. Then he gets up and does what I say but with a lot of back talk under-the-breath, “Maaaaan, watch, I ain’t scared of you” and so forth and so on. Then mom steps into the room in a meek, mild, teary-eyed manner like she’s afraid of what he might do and starts chastising me for my way of discipline when like 4hrs ago she agreed that that was what we needed to do. So whenever there's a new situation with him like he wants money to go shopping or anything, he'll go to her. Without any pre-conditions or anything she’ll give him what he wants and then I’ll step in and ask her, “What did you give him that for when he didn’t take out the garbage” and then she’ll start screaming and yelling at me. Or, in some instances get naïve and bubbly-eyed with me and say, “Oh, I didn’t know just leave him alone.” So here we have arrived because she wants to hear what an expert has to say.