If you two cannot agree on a split, then you have to ask the courts to decide the issue for you.
For the amount involved here, small claims would not be an option. You would need an attorney, probably a real estate attorney.
Courts usually decide these issues by ordering a partition sale. Unfortunately, a partition sale is akin to "a fire sale". The vultures will be out and you two won't be able to sell the property for anything close to what you think it is worth, even without considering your respective legal fees.
I am not saying your interpretion of what the law says is incorrect. What I am saying is that enforcing your point of view likely is going to be costly if you truly want to sell the property and you cannot reach an agreement with him. Of course, it will also be costly for him to use the partition sale route.
What I am saying is that you two can agree to something that is less than a 50/50 split, but don't sign anything, including a quit claim deed, until you get whatever money you agree is your share. You don't necessarily have to agree to everything he is proposing. (Remember, if he had really wanted to go the partition sale route, he probably could have tried it shortly after you two broke up. He probably soon figured out it was not a good idea.)
Therefore, you are not without your own negotiating power here. If you are not comfortable with negotiaitng this one yourself, then you might want to consider hiring an attorney as this is something most attorneys do on a regular basis.