I just want to know what I can do to show him I'm serious about not putting up with this anymore.
YOU can show him you are serious by upholding your threat. Clean up by December or I'm done. If you are not done, you are showing him that you are NOT serious about it what so ever.
I can't imagine going through all that while pregnant. I am glad you found us - we understand, we've been there or are there, and there is a tone of support here because of it.
Do you have some local support for you? Can you get to an Alanon meeting? The only people you can help in your situation are you and your kiddos. Much love to you guys.