Or u guys can just strictly communicate through email.
As long as he is going to be part of the kids like and spend time with him on his own, you should give him your number. Hopefully nothing ever happens, but on the slim chance it does, do you really want to wait till you finally get the message as you are playing phone tag with his mom. Not too mention what happens if for some reason she does not have her phone with her.
I honestly feel the same way you do. My son's father wrecked my whole pregnancy.. I'm 33 weeks and JUST left him yesterday. I know I have a long road of sadness but I know one day, I'll look back and know that what I did was for my son. He doesn't need negativity in his life.
Or through text, I think he should be able to keep in contact with u as u r carrying his baby. He has a right to know. Make sure it is only any about the baby and what is happening and nothing else but your baby will need it's father as long as he is a good parent. He may have been not so good when u were together but it could be different for your child.
I would allow him contact if it were me