I'm so sorry you're going through this again and at time when your thoughts and energies should be focused on your baby.
Keep your physical health your main priority. Get as much rest and relief from this crazy mess as you can. Eat right and drink water...contact your doctor if you need to.
As far as your WH goes, he admits (and OW seems to confirm) that it was him who broke the NC by contacting her, supposedly to find out if she delivered her baby. Also, with your first DD, OW said she was pregnant (from another man), told your H and he had a breakdown where he confessed the A and threatened suicide? Is that right? I think there is a very real possibility that the child is your Hs - I think you have to prepare yourself for that possibility. I think either way the paternity issue is weighing on you H.
You need to contact a lawyer right away. You need to explain everything (particularly the questionable paternity), and find out what your rights are as a spouse with a child. You need this information to protect yourself and your baby and other children.
Also, your H set up a new email account to be in touch with OW! They are communicating on a regular basis and she used these emails to pressure him or embarrass him to his family. It seems the A between these two may have never really ended, that they just took it underground.
I think for your sanity, you need to kick him out and begin the 180 process. Read up on it and remember the 180 is about YOU not HIM.
Honey, this is awful...stay strong and continue to get as much help and support from your mom as you can. Post back here and let others help you through this.