What is your plan for after you tell him? Are you planning on cohabitating with him and your child?
You have given an attorney a retainer, has the paperwork been drawn up and ready to be served to him?
You sound like you have done some planning but have you thought this all the way through? I mean the telling him right now today part?
Life after this conversation will never be the same and if he’s vindictive then maybe you need to rethink some of this planning.