All the subjects you refer i.e., divorce, child custody and maintenance are under different provisions of law, hence all are different subjects. Though you file all of them together, they will be treated as separate cases only.
The divorce shall be filed under the provisions of Hindu Marriage Act, child custody case under Guardians and Wards act, child maintenance under HAMA or 125 Cr.p.c. So they are to be filed separately though in the same family court and simultaneously.
Your earnings shall be a question of argument while the maintenance case for your child's maintenance is heard by the court, so there is nothing wrong in filing it , let the court decide based on the merits and arguments presented before it by both the parties.