You should not leave. You are the wife and woman of the house! If anyone leaves it should be SS. He is almost grown and needs to decide what he is going to do with his life - school, military, etc. Your DH needs to explain this to him. Then you and DH can go on as the newlyweds you are!
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Age cannot wither her, nor custom stale
Her infinite variety.

William Shakespeare, "Antony and Cleopatra", Act 2 scene 2

no one can tell you where to leave or stay. i would not continue to live like that. my sd and her two children lived with me and her dad for 2 1/2 yrs until i decided she had to go and as much as i loved him and wanted our marriage to work i couldn't take it anymore. i had decided she was going and he would make up his oun mind wheather he wanted to go or stay.
at that point it didn't matter because if something didn't happen it was going to ruine our marriage anyway. he stayed and to this day she still don't have it together but i refuse to let her make me miserable. i wish i had more time to go into things. i know you love your husband but you also have to love yourself enough to not allow anyone to treat you this way. i felt like my husband was mistreating me as much as the sd for allowing it to happen. my prayers are with you.

In a different thread W23 said "I told DH "I didn't marry you because you had kids, I would never leave you because you have kids." "

Don't leave because of the Skid. That does not mean that you should tolerate the bullshit the kid is putting you through. I would let DH and SS know in no uncertain terms that any repeated instances of the theft and substance abuse behavior will put SS in jail and you will call 911 to have him hauled off.

No ultimatums about you leaving, just a clear statement of exactly what the consequences of SS's behavior will be. Then follow through. You may also want make DH clear that HE should be the one calling the Police to have SS hauled off to jail. It will make a significantly more substantial impression on SS if Dad is the the one that holds him accountable for his actions rather than the WickedStepMother.

The next time he threatens to kill himself have the little white van with the big burly guys is white outfits put him in a straight jacket and haul him off to the Mental Hospital. DH can sign the commitment papers since the Skid is a minor and suicidal.

At 17 it is not difficult to initiate a forced emancipation if SS thinks his behavior is appropriate and can handle life on his own. If he does not pull his head out of his ass pack a small dufflebag for him, hand it to him, pat him on the ass tell him to write when he has a job and an address that you can forward his mail to.

Good luck and best regards,

Success is rarely final. Failure is rarely fatal. It is character, courage and consistency of effort that count. Vince Lombardi (with some minor Rags modifications) To each according to their performance, screw Karl Marx. (Rags)

I'd kick him out. He has no right to come into your life and cause hell.