Not to mention, you’d have to ship either the boxes, or Lobelia, over the pond for this to work out.
Now, being a tiny bit of a devil’s advocate here, it’s not out of line for the brother to want to stay with the family when he comes for a visit (though he should be happy to bunk on the couch vs expecting rooms set aside for his personal use).
Or, rather, it wouldn’t be, if he weren’t abusive!
Given his threats to you in the past - and if you haven’t documented them, start doing so now - I’d be leery of letting him in the house.
Given that the OP mentions the Gardaí and €, my own € say she’s in Ireland.
Lobelia, I do think you should call Social Services, see about getting a power of attorney (SS may be able to help with that, their Spanish counterpart brought it up with my cousin re. the Grandparents), and verifying whether that second will really is void and what happens in that case when your mother dies, if she’s considered intestated at that point.
Is it possible your mother already has her own will in place, made back when your dad made his will and possibly before the dementia? That was the normal course of events when my ex and I made our wills…we went together and the wills covered all the contingencies. After my dad died, my mom didn’t necessarily NEED to make a new will, since hers was fine, but she did just to change guardianships of us kids since we were all adults by then.