Ask HN: How to get rid of a bad gut feeling / co-founder?

One year ago i had an idea and decided to found a startup. But i made a big mistake. A got a co-founder on board while having a bad gut feeling. He is a business guy and we already worked a few years together as agency (he) and freelancer (me, designer). He still runs his agency full-time while i am working on it 30h/week (while studying and working). I have 2/3 of the shares. He has round about 1/3. But we wrote nothing down and the company is not founded yet. He is round about 10 years older than me (i am 21). There are a few things which makes me nervous: i have had a bad gut feeling from the beginning, i do not trust him and it blocks and demotivates me to have him in the team. He is lazy (regarding our startup) and it feels like having a shark on board. First i tried to get rid of him six month ago. It didn't work out. I told him by phone that i can not do this with him. That i have a really bad feeling and do not want to do this with him. That i like to work with him but that we have two different views on entrepreneurship and how to build a startup. He threatened with a lawyer and said that he promise to "destroy" me when i would do this. He added two persons to the team, tried to create a partnership and wrote round about 20 lines of the business plan. Nothing more, in one year. Now, six months later i begin to struggle again with the fact to have him in the team. It blocks me mentally. It demotivates. It feels bad. We are two months away from our launch and i really need some advices how to handle this. Should i contact a lawyer? Should i just say "Goodbye" and hang up the phone? What do you think? The best thing would have been to listen to my gut and havn't let him on board, i know.