Where are you located? If on the North Coast, there is a labor office in Puerto Plata.
To avoid payment of all but the things you have no choice about, such as days worked, but not yet paid, before discharge and a portion of Christmas and vacation pay for the months worked in 2010, you should try to fire him and avoid payment of severance. There is a procedure for firing somebody that requires I believe 3 notices in a month of violation of work requirements, with copies of these notices filed in the labor office.
You should find out exaactly what this procedure is, then decide if you want to try to fire him without paying him anything but the things mentioned above. Unless you fire him with cause, you will also have to pay him a sum based on time worked and salary and this is the Dominican version of unemployment benefits in that it is supposed to help the fired employee exist until he gets another job.
Check it out. You may be able to save some money by giving him another month and using the time to build a file to show that you are justified to file him for cause.