fis or opfp

I am a newly single mother of 2. I have recently returned to work after mat leave to do part time hours ( 20 hrs per week). Myself and the kids father were never married but we had/have a mortgage. The relationship ended 2 months ago. He moved out but continues to pay the mortgage as he always did. I was ok for money while on mat leave as i was on full pay. Now i find myself struggling with €220 per week. It was suggested to me by a friend that i should apply for FIS, which i have. I figure if successful i should get 60% of the diff between €220 and €605 which is about €170 pw. Obviously a HUGE help.
Then while i was looking on welfare.ie i came across opfp. Should i have applied for this and not FIS. Will the FIS people say apply for opfp first and then FIS. My question is, will the fact that i haven't applied for opfp stop them processing my FIS application?
Also the fact that the kids father is paying the mortgage straight into the mortgage account but not paying maintenance, will it count as maintenance? If it did it would make a huge difference to what i would be entitled to.
Any help would be greatly appreciated.

You can apply for both OPFP (one parent family payment) and FIS (family income supplement).

Any FIS received won't be assessed as means when carrying out the means test for OPFP.

FIS section won't delay your application because you haven't applied for One Parent Family payment, although they might let you know that you could apply for it.

For OPFP, a person is allowed to offset a certain amount of maintenance against housing costs (95.23 per week), and half of the remainder is assessed as means.

You should declare the fact that the mortgage is being paid as a form of unofficial maintenance (assuming there is no court order or similar arrangement).

gipiman thanks so much for your reply. It was stressing me out all day. I rang citz info and the lady i spoke to didn't understand the question and then i rang the FIS crowd and i was on hold until my credit ran out!.
There is a part on the FIS form that asks who is paying your mortgage if its not you, so i put down my ex partners name and the amount he is paying which is €225pw. Will this be counted as weekly income to me?
Thanks again.

The FIS information page on www.welfare.ie states that

Income from any source (excluding the disregards stated below) is assessed as means.

There is no disregard for maintenance (or the equivalent of maintenance, which the mortgage payment from your ex appears to be), so it's likely that it will be assessed as income.