According to this fun little utility, Mr. Crab has now visited 41% of Europe. Although in reality, it's probably more like 61% because the site counts small city-states like the Vatican and Monaco as equals to "real" countries like Russia. Most of the states remaining on my list are in Eastern Europe. If you add the countries both Crabs have visited, it goes up to 50% or so because Mrs Crab has also been to Luxembourg, Iceland and even a country which no longer exists: Yugoslavia.
I've also updated our world map, which suggests that Mr. Crab has visited 44 countries, or barely 19% of Planet Earth. It's a big world. Get out there!