Trim the crusts from the bread; discard, or reserve for another use. Tear the remaining bread into little pieces (about 20 pieces per slice); handle the bread lightly, so the pieces remain fluffy and don't flatten out. Place the bread pieces in a bowl, and sprinkle them with the wine; toss lightly to distribute the wine evenly.
Pick over the backfin and the jumbo lump crabmeat to remove any bits of shell. In a large mixing bowl, toss together the backfin and jumbo lump crabmeat. Season to taste with salt and with Maryland crab seasoning. Add the soaked bread, beaten eggs, lemon juice, and melted butter; toss lightly, making sure to keep the crab lumps whole. Add the mayonnaise, and toss the mixture gently with your hands, distributing the mayonnaise evenly. Taste again for seasoning, if desired (if you don't want to taste raw egg, you can saute a bit of the mixture in butter). For even better flavor, allow the mixture to sit in the refrigerator for a few hours.
When you are ready to cook, place a large, heavy-bottomed saute pan over medium-high heat; the pan should have enough room for 3 crab cakes. Add enough lard and vegetable oil (in fifty-fifty production) to create a 1-inch depth of oil. When the oil is medium-hot, quickly shape 1/2 the crab mixture with your hands into 3 cakes, each roughly the size and shape of a large hamburger. Gently place the cakes in the oil, making sure to preserve their shapes. Fry for 3 to 4 minutes, or until the cakes are golden on one side. Flip them carefully with a spatula, and fry on the other side for 3 to 4 minutes. After about 8 minutes, the cakes should be golden brown on all sides and heated through (you want the pieces of bread inside to virtually disappear). Remove the cakes from the pan, and place them on paper towels. Repeat and make 3 more cakes with the remaining mixture.