Bring a large pot of water to a boil. In a small pot, steep the saffron in the stock over medium while you make the sauce.
In a large saucepan, heat 2 tbsp. EVOO, two turns of the pan, over medium-high. Add the leek, fennel, onion, carrot, celery, thyme, bay leaf, crushed red pepper and half the garlic; season with salt and pepper. Cover and cook, stirring occasionally, until the vegetables soften, 8 to 10 minutes. Add 1/2 cup wine and simmer 1 minute. Add the tomatoes and bring to a bubble. Add the saffron stock and let the sauce simmer while you cook the seafood.
In a large, deep skillet with a tight-fitting lid, heat the remaining 2 tbsp. EVOO, two turns of the pan, over medium-high. Add the clams, shrimp, squid and the remaining garlic; season. Cover and cook until the clams open, shaking the pan occasionally, 5 to 7 minutes.
When the water comes to a boil, salt it, add the pasta and cook until al dente. Drain, reserving 1 cup of the pasta cooking water. Return the pasta to the pot.
Add the remaining 1/2 cup wine and the lobster to the seafood mixture; douse with the lemon juice. Toss the seafood and half the sauce into the pasta, adding reserved cooking water, as needed, if dry. Transfer the pasta to bowls. Top with a little more sauce and pass the remaining sauce at the table.