Firstly, take a look at your tax position and get some professional advice as to whether or not you have everything set up in terms of credits and what you can claim for and whether or not you can do a claim for past years
Sell the rental, that's harsh on the current tennants but such is life and you need to prioritise yourself and your family. You earning 800 a month in rent on an asset that is costing you 1330 in mortgage payments and tax. Including the prize bonds, you'll have around €150k to invest, either by reducing your current mortgage or doing something else with it. 25k in what in essence are raffle tickets makes no sense
You then won't need to save 500 per month to cover the rental tax and you will see a difference once that happens.