Hi
Looking for help

Background :

Married 5 years in Sep to the love of my life. Been together 9 years
3 Biological Children ( daughter 21, son 18, son 16)
2 Step Children ( daughter 20, son 15)
2 step children live with us full time
16 son lives 7 days with us then 7 days with his mom)

In a nut shell our 15 year old stepson is causing major problems in marriage.

I am going to bring up today's events as they are fresh in my brain.

Today we moved our stuff from one storage to another.

Present is my wife, 20 stepdaughter, her boyfriend, , 15 stepson, and me.

Stepson basically starts talking extremely disrespectful from the first minute we were there.
Questioning every single thing we do. Cussing, staring us down, basically acting like a little punk.
He talks rude to everybody. My wife kept telling him to stop, but he does not listen to her or anybody else.
I finally yelled at him and told him to stop in which he cussed at me.
Mom told him to stop too or he wasn't going to movies this evening.
He didn't stop. He never does. I am tired if it.

My wife and I went to return the U-haul we rented. On our way back home we talked about the days events.
I asked her if it was okay with the way he acted. She says absolutely not.

We get home, take showers, etc.
she starts getting dressed to go somewhere.. I ask where she's going , drop off stepson at movies.....

I said REALLY ?? After all that ??

She drops him off.

When she gets back I ask her if she is going to discipline him.
Is she going to hold him responsible for his actions????

We end up in a yelling dispute. She slaps me.
I don't get it .

She will not discipline him or hold him responsible for anything he does.
She always says she talked to him , but nothing changes.
It seems like she is scared to discipline him.
This is nothing new. He brags that he has his mom wrapped around his finger.

Whenever I try to talk to her about him she does a couple things:
1. Blames it on another child or me.
2. Makes excuses for him.
3. Gets angry at me.
4. Won't talk, ignores me like I'm not talking.
5. Gets angry at me and threatens divorce.
6. Mimics me.
7. Says other kids do things at dont get punished.

Now with that said, I know she loves me. No doubts at all.

Just when it comes to stepson it's like she just blacks out.
She just can't control herself.

An hour later I try to talk to her and she's still ignoring me like a 4 year old throwing a tantrum.

I need help.
I can't allow stepson to cause all these problems.
It's absurd.
It's always someone else's fault when he does something.
(FYI stepsons dad is out of picture, hardly any contact before me, couple years later no contact at all
This dude even named his new son with new wife exact same name as our stepson --major loser)

This is not a one time deal.

Happens a lot and we only have these types of arguments when it comes to stepson.

Any constructive help would be appreciated.

Thanks Jerry