Have you considered an AJP riser rail to give you a bit of height so you can use the mounts in your photo? Well it'll get you over you 'A' problem anyway.
Don't have any suggestions for a one piece mount with a distance greater than 110mm sorry
I use two piece mounts on my boinger and they haven't moved. The AJP rail I've got did, but that was down to me not tightening it up sufficiently to grip the dovetails