You will get the Homecarers allowance for the first year that she goes back to work, you only lose it in year 2. If your wife was in receipt of other benefits you may qualify for Job Assist Credit, worth checking out.
In relation to Cut-Off points, for married with one earning, it is €43k @20% and balance at 41%. If both working, it is 43k @20% with an additon of up to €25k for the second earner (restricted to the level of earning of the second earner) @ 20% so up to max €68k @ 20% and balance @ 41%. So for poster 3, the max is €43k plus €5k @ 20% and the rest at 41%.