Is there some reason you are discussing this with your Dad? If he thinks it's a great idea and then finds out it effected your marriage he will feel responsible. You need to work this out with your DH and leave him out of it. One thing is you are going to be equal partners with someone you were superior to in another job, sometimes that is awkward. What has stopped you from being your own boss? Your DH sounds unreasonable, but hey if you think it isn't worth risking your marriage then stop contemplating the partnership. You know if there are other red flags.
My dad is the smartest and most successful person I know. He's developed several successful businesses. I'd be discussing the business aspects with him. I'm not planning on sharing all of the details of my marriage with him.