Prepare the Crab Stock: Use your hands to break crabs into quarters, removing and discarding the gills and reserving orange fat and roe (about 3 tablespoons) for Crab Butter. Cook crab quarters in hot olive oil in a Dutch oven over high, scraping any browned bits off bottom of Dutch oven. Reduce heat to medium-high; add onion, celery, and carrots, and cook, stirring often, until softened, about 5 minutes. Add tomato paste, and cook, stirring often, 2 minutes. Stir in tomatoes, and cook, stirring often, until tomatoes break down, about 4 minutes. Add wine, and cook until reduced by half, about 5 to 6 minutes. Stir in water, and bring to a boil, skimming off any foam that rises to the top. Reduce heat to medium-low, and simmer, uncovered, 45 minutes. Pour mixture through a fine wire-mesh strainer into a bowl, discarding solids. Return stock to Dutch oven, and cook over high until reduced to about 2 cups, about 20 minutes.
Prepare the Crab Butter: Melt 1 1/2 tablespoons unsalted butter in a medium skillet over medium; add jalapeño and shallots, and cook, stirring occasionally, until very soft, about 6 minutes. Stir in wine, and cook until liquid is reduced and skillet is almost dry, about 8 minutes. Remove from heat, and cool completely, about 20 to 30 minutes. Stir together cooled jalapeño mixture, reserved crab fat and roe, lemon zest, and softened butter in a medium bowl until blended. Cover and chill 20 to 30 minutes or until ready to use
Prepare the Pasta: Cook pasta according to package directions. Melt 1 tablespoon of the Crab Butter in a large skillet over medium-high; add jalapeño and shallots, and cook, stirring often, until softened, about 4 minutes. Add crabmeat, and toss until thoroughly heated. Add cooked pasta, Crab Stock, lemon juice, and salt. Bring mixture to a rapid boil, and add remaining Crab Butter, tossing pasta until butter is melted and incorporated into the sauce. Stir in basil and scallions; serve with lemon wedges.