Is a rotary hammer with an impact energy of 2.7J suitable for household projects?
That is not a huge area to break up. I would say if it is not reenforced you should be able to drill a series of holes and break it up, 

I might get a masonry blade for a skill saw and cut channels then a sharp smack with a hammer it will crack into blocks.

I have wedged the edge of 6” slab off the ground then used a lead cannon ball (down rigger lead ball 35 lbs) over my head and slammed onto the slab to break it up with no drilled holes or saw cuts. Concrete is very brittle if not supported. 

A few drill holes will help to guide the breaks and then you have manageable sized blocks to work with And possibly reuse. 
I have 3 or 4 hammer drills and to tell the truth they all work about the same except the hilti that is really not a drill / hammer drill but a hammer drill only. So if you purchase the Bosch you have a tool with multiple uses around the house, makes sense to me.