Here is how Maintenance is assessed for One Parent Family Payment:
All income from maintenance is assessed as means. This includes maintenance for you and maintenance to you for any of your children. If you are getting maintenance from more than one person it will be added together and the total will be assessed as means. However, your rent or mortgage repayment up to a maximum of €95.23 per week can be offset against maintenance payments. Half the balance is then assessed as means and your social welfare payment will be reduced by that amount. You must provide proof of rent or mortgage payments.
Based on the above calculation and the figure you supplied, your means from maintenance would be approx €182 per week. The OFP rate for one adult and 4 children is €307.20 so depending on your circumstances, you may have an entitlement.
Maintenance is counted as income for Medical Card applications, but there is an allowance for mortgage paid.
You should make an application for both items.