You have several issues to deal with here. I am guessing that you had an attorney represent you at the initial restitution hearing - you should start by contacting him/her and asking about the differing amount. If the numbers truly don't add up and the victim is cooperative ask your attorney about going back in front of the court to correct the amounts owed.
As far as a civil judgment is concerned - well that is exactly what is says on the tin - a civil judgment, so the criminal law section is probably not the best place to get an answer. With that being said, the answer to your question is "yes" the could force the sale of your house to satisfy the judgment. However, that is a fairly complex process and is dependent on numerous issues - how much equity do you have in the house, the amount that you can claim as an exemption, how many other liens are on the property, just to mention a few. With a civil judgment they could also levy on your bank accounts or garnish your wages, they could also seize and sell your car or any other property that you own - but all of that is speculation.
Start with your first issue, lock down the amount owed. Then move on to the repayment aspect, can you make a deal with the victim for a payment plan, etc., etc.
However, your first move should be to speak to an attorney - start with your original attorney, if they are unwilling or unable to help, use the search feature here to locate someone local that works in the civil arena, specifically someone that is familiar with judgment enforcement.
Good luck to you.
This answer is for general informational purposes only and shall not constitute legal advice. I have answered a question on a public forum which does not establish any attorney-client relationship. For a more detailed legal analysis you should consult with a legal professional in your area.
Start by talking to your original attorney. If he won't help or if you don't like what he does or says, look for a new one.
The response above is not intended as legal advice. This response does not create an attorney-client relationship. Legal questions can only be fully answered through consultation with an attorney to whom you give full and accurate details. Anything you post here is not confidential and is not protected by the attorney-client relationship. It is highly recommended that you seek advice from a criminal defense attorney licensed in your jurisdiction by setting up a confidential meeting.