The obligor is the one who pays child support (your husband) and the obligee is the one support is paid to.
I'm afraid I've never been successful taking any of my medical expenses into account. Yours have to be astronomical after a transplant. I'm guessing around $250,000 at least?? If that is the case, talk to the lawyer about asking for an exception. It's not guaranteed in any way, but I'm sure you could ask. I believe there is something about the support can NOT put you below a certain standard of living. If you can prove the medical expenses combined with the child support put you below this level, then the courts may grant an exception.
Also, you may want to talk to Social Security. Because of the changes in the law, the derivative benefits check should probably NOT be going directly to their mother any more. Ask the lawyer about this.
Finally, if you feel like the lawyer does not understand these issues, then move on and find one that does.
Good luck to you and your hubby! Sending prayers for his health....so difficult I'm sure and dealing with all of this can not be helping.