I think you'll find the behavior will just go more "underground" but won't stop.
I also agree with above poster that you, at least, should have your money
and assets not difficult to access but impossible to access legally by him.
You sound really saavy to many of the tricks,
but addicts are extremely resourceful at finding ways to get their drugs.
Don't underestimatethat, or the cravings he will be having,
since it appears he's been using regularly for some time.
Sometimes they steal small valuables to hock so do lock up your jewelry for now,
even if it seems like overkill. Too late when it's gone.
Review what other things you have that might vanish without you noticing for awhile and keep track.
Most addicts can't just "stop" without some extra support and most of the the strong willingness to do so.
Right now he's been caught, as someone said, but that doesn't mean he's done.
His sister taking you aside and warning you should be a huge flag that this
could, and maybe has, been a very bad issue in the past.
Part of your discussion about finances maybe needs to be
what external support / steps he plans to take to get help to really stop.
Actions speak louder than words, and so far they have.
He's stealing from the family, lying to you and impersonating you to get
access to your credit, and he apparently wasn't honest enough to tell
you about his addiction, or the depth of it, before marriage.
I'd say he needs to show you though actively engaging in a treatment program
and total financial accountability that he really is serious about not using again.
I'm sorry you are dealing with this with a little one on the way.
You really sound smart with a good head for finances and solid self-esteem.
These are great qualities for anyone, but especially in this situation.
He's already stepped over you boundary more than once.
What's your plan if he does so again?