I don't think it's a good idea to rent out your house while renting something cheaper yourselves, as the difference will be easily swallowed by extra expenses - letting agents fees (if you use an agent), PRTB registration fee, NPPR charge, insurance, repairs and tax. Only 75% of the interest is tax deductible, so even if your rental income just covers your interest payments, you'll still have to pay tax...
In order to pay tax, you'll need to file a tax return each year - are you really prepared for that, with the new baby coming etc? If you can't do it yourself, you'll need to get an accountant to do it - extra expense...
And so long as you rent out your house, you run the risk of getting a bad tenant who could cause huge financial damage to you.
I think you are really better off moving into your house yourselves, and maybe renting out a room under rent a room scheme to bring in some extra money. (Though you'll still need to file tax returns for rent a room scheme, but at least they are more straightforward and no tax to pay.)
And coming to an agreement with your bank regarding your ability to repay your mortgage and loan. You should also contact MABS.
Have you any family in Ireland who can help you with the baby so that you will be able to go back to work without paying a fortune for childcare?