Dened - you don't sound hysterical to me, nor do I think you need to work on your "jealousy".
I do know women who need to work on their jealously. They are the ones who either stop their exs seeing their own children at all, or the new wives, who put intesne pressure to bear on their new husbands to stop them having a relationship with their kids from past relationships. The number of absent dads who lose contact within a year or two the split is huge - so the fact that he has contact, and that your only complaint is that he is sharing a bedroom with his ex (FFS - angry is normal about this!!) demonstrates you are well within the range of normal, balanced and decent.
I took your suggestion that you felt tricked into sending the text to mean that it isn't the sort of thing you would normally do. While I would reserve 99.9% of my annoyance for DH, I also feel this woman hasn't been very respectful of you. If an old bf of mine was just married, I wouldn't want to sleep in the same room as him. I certainly wouldn't follow it up with a rude text saying I would call him when ever I liked.
I wouldnt' read too much into the police involvement. Telling her not to contact him except in emergencies and you not to send abusive texts is the equivalent of knocking heads together - if they really felt you had donce much wrong, they could have cautioned you for breaching teh peace or threatening behaviour.
Your real problem is that your ex and his ex-wife don't have boundaries in place that most other exs would have. You can't expect her to do anything for your marriage (why should she) - so you need to urgently sit down with your DH and discuss your expectations. Even if he has other families, you still have a right to a private family life of your own. Think about what you need, and what is possible.
For example, she may contact him half a dozen times a day, but he doesnt' need to reply!
Having DCs is an irreversable step, so I think you are right to wait until things are on an even footing... however, if he has unstable exs, you may find that your pg will set them off again.
Only you can judge if he is worth it - good luck.
PS, you can't divorce him until you have been married for at least a year anyway, but if you do decide to, you might find the defintion of "Starter Marriage" makes you feel better.