Need help with step son and mother?

After 8 years of marriage to a woman with a child, now teenager, at home who basically has to be entertained practically everyday I am getting my fill, as a matter of fact my cup is overflowing. He's ungrateful and no matter what he gets, which is just about everything he wants, it's never enough. He can basically do no wrong in his mothers eyes. I"ve seen aspects of his character for quite sometime and when I mention it to her I walk away a bloody mess, not literally, but emotionally because I've said something negative about her little prince. Sad to say, the good part is that in the past six months she's caught him in a number of lies, has found drug paraphernalia several times, and have seen him come in loaded from smoking marijuana. And yet, when I catch him in a lie and say anything, once again I come away a bloody mess. It's never his fault, it's always the guys he hangs out with. We've moved to get away from it and in a matter of a week or so it's the same thing all over again. Our whole life seems to center around him. If there's something we want to do as a family we can't because poor baby hasn't had enough sleep and to have to get up in time would be too much for him. And yet, if it's something he wants to do he will fly out of bed, even two hours earlier than usual and run out without breakfast. This, for some reason I have a hard time swallowing and yet to say anything I get ripped. Now, I should always be available to take him wherever he wants to go even if it means I have to be late for an appointment, or have to give up something I had planned because it's a new day and baby boy (16) must have all his "wants" met. My wife and I have to live tight because we spend so much on him that we can't enjoy anything ourselves with the exception of "maybe" one dinner date a month and that doesn't always happen. I could go on but I think you get the point. I am so sick of living like this. I don't believe in divorce and I know life will be much better in two years when, hopefully, his a-- will be out of the house. Do you have any advice? And please no smart a--es, I already have to live with one and if you haven't anything intelligent to say then don't say anything.