Put the potatoes in a small pot, cover with water, and bring to a boil over high heat. Salt the water and cook until tender, 10 to 12 minutes. Drain, then return the potatoes to the pot and mash.
Meanwhile, put the salmon fillets in a skillet with the wine, bay leaf, and enough water to come up to the top of the fillets, but do not cover. Bring to a boil over medium heat, then reduce heat to a simmer and poach until opaque about 8 to 10 minutes. Remove the skin and transfer the salmon to a bowl. Flake the fish with a fork and season with salt and pepper, to taste. Add the mashed sweet potatoes to the bowl along with the seafood seasoning, half of the cracker crumbs, the egg, thyme, hot sauce, scallions, and dill. Mix to combine. The fish cake mixture needs to be just firm enough to mold into cakes. If its too wet, add a few more crumbs.
Heat 2 skillets, side by side, 1 with 2 tablespoons extra-virgin olive oil (2 turns of the pan) over medium heat, the other with 1 tablespoon extra-virgin olive oil (a turn of the pan) over medium-high heat. Form the salmon mixture into 4 (4-inch) patties, coat in the remaining crumbs, and then add them to the first pan. Cook the fish cakes until light golden, about 2 to 3 minutes on each side. Add the red onions, celery, and garlic to the second pan and cook 3 to 4 minutes. Add the tomatoes, season with salt and pepper, to taste, and cook 2 minutes more. Stir the vinegar into the sauce, then sprinkle the sugar over top and toss to coat the tomatoes. And arugula.
Arrange the fish cakes on individual serving plates alongside the arugula. Top with the agrodolce relish and serve.