So I just read this HN posted article (The 7 Habits of Highly Overrated People - https://news.ycombinator.com/item?id=6965295) and thought a lot about my co-founder who is doing jack shit in the company. I already talked to him about lowering his share options (which he currently holds about 40%, (same as me, after seed round dilution)), but with no avail. He actually threatens the company's success if I ever try to "sneak a move" on him when in reality his contributions are near 0 for product development as well as S&M.
If I talk with my boards on his misbehaviour it will get them stressed and stop believing on the company. Is there really no way to fire him and the only way is to actually quit ?
Sorry dude, looks like that is precisely what you are going to have to do. Don't worry about the board stressing; they can handle it. That's their job.
Focus on YOUR job: the success of the company. The board will stop believing you when you prolong this longer than you should have, actually making the situation much worse.
When you go to the board, GO PREPARED. Assume the board does not know anything. And treat it almost like a trial where you will get to present your side, and at some point, your co-founder will get to present his. In these cases, I like to open up a document and put down the facts in bullet points. When presenting, remain calm and stick to the facts, which when evaluated by a sensible party(your board), should have them arrive at the same conclusion as you.