Both reports you got were wrong.
If you go back to work, you will lose your rent allowance in full. Your wages will be taken into consideration and you will loose, depending on how much you earn not how many hours, of your OPF. Once you have informed SW by getting letter from your employer on how much you get paid (gross) then you apply for FIS.
Apply for FIS after your OPF has been adjusted if at all. You need to be working a min of 20 hours per week to qualify.
FIS is the only social welfare payment based on a minimum amount of hours you have to work to get it. The office is based in Longford, but you have to be working 4 weeks before you can apply anyway.
You may also keep your medical card, depending on how much your weekly income is - childminding costs, rent and travel expenses are also taken into account.
If, however you go on a scheme - eg Fas or Back to Work Scheme, then you keep a percentage of your OPF, your full wage, rent allowance and all other entitlements. You can also try to apply for FIS.
When you cease employment, providing you have enough stamps, you can claim unemployment assistance at half rate for 15 months along with your lone parents.
Hope this helps...