I have to agree with a lot of the responses that you have gotten so far. I would not have paid him anything since the work was not authorized and I definitely would not pay him anything else.
Actually you may want to contact a lawyer or do some research on your own. I believe that all auto shops are REQUIRED BY LAW to give you a WRITTEN ESTIMATE before doing any work on your vehicle...with the exception of say an inspection.
I have lived in a lot of different states and I know that everytime I have ever taken my vehicle anywhere to have work done (with the exception of say oil changes and/or tires rotated etc) there has always been a written estimate of charges BEFORE any work has been completed and I have always had to sign that estimate either approving them to do the work or declining the work to be done.
I would not pay this guy anymore money until he can provide you with the signed estimate and authorization to do the work. I would also let him know that if he wants to take you to court he is more than welcome to do so and that you will be filing a counter claim.
Totally sounds like this guy is totally taking advantage of the fact that you and your husband obviously have NO mechanical knowledge at all. (Sorry but it is pretty easy to identify the sound that brakes make when they are going bad, so if you are unable to do this then your mechanical knowldege is very, very low.)
Therefore he is using your lack of knowledge to take full advantage of you.
Don't pay him another dime and quit taking him phone calls.
Good luck!!