You are right, the Florida divorce forms needed for a dissolution of marriage with minor children can be confusing and time consuming to complete.
To answer some of your questions, you will want to complete the financial affidavit with as much accuracy as possible. Any expenses for the minor child would go under that section and if you have other expenses you can place them on the blank lines provided for you on the form.
If you are asking for your husband to be responsible for the IRS fees, you could place them on the "Other" section of the petition, in addition to listing them on the Financial Affidavit, and checking in the box stating that you request the judge to hold husband responsible for the debt.
As for the child support guidelines worksheet, you would simply fill it out based on the information contained in the financial affidavits and if applicable, complete the further calculations if there is substantial time-sharing between the parents (73 overnights or more per year).
If you need assistance completing the forms, please feel free to PM me. I am an experiened legal document preparer in Florida with over 9 years of experience. Good luck!