Of course they are but you better get some medical background too if you want to be good at it. (the medical malpractice part anyway)
Medical malpractice is a highly specialized area to focus in. Personal injury, in general, is not as specialized. PI cases can range from dog bite cases that pay beans to fatal car accident cases that can bring in a lot of money.
Here's an attorney website for an example of medical malpractice: http://www.drslawfirm.com/medicalmalprac...
Chances he can get any custody after six years: highly unlikely. First thing the judge will say is, "Where the heck you been for six years?!"
He can probably get a visitation order, which you should do your best to support, for the sake of your child.
Child support amounts are set as percentages by statute. A modification can be requested, but support orders can only be changed if there has been a substantial change in circumstances: an increase or decrease in either parent’s earnings, a change in custody, or a change in the amount of time the child spends with each parent.
Unless his income has been more drastically reduced than yours, it's actually more likely his support payments will increase.
Barring anything else, sounds like all you have to do is show up with your income info, and be just as gracious as you can pull off at this point. ;)