Process bread in food processor until finely ground (you should have ¾ cup crumbs). Combine chickpeas and broth in large saucepan and bring to boil over high heat. Adjust heat to maintain simmer and cook until level of liquid is just below top layer of chickpeas, about 10 minutes.
While chickpeas cook, heat ¼ cup oil in 10-inch nonstick or carbon-steel skillet over medium heat until just shimmering. Add bread crumbs and cook, stirring frequently, until deep golden brown, 3 to 4 minutes. Add garlic, paprika, cumin, salt, cinnamon, cayenne, and saffron and cook until fragrant, 30 seconds. Stir in tomatoes and vinegar; remove from heat.
Stir bread mixture and spinach into chickpeas. Continue to simmer, stirring occasionally, until mixture is thick and stew-like, 5 to 10 minutes longer. Off heat, stir in remaining 2 tablespoons oil. Cover and let stand for 5 minutes. Season with salt and extra vinegar to taste. Transfer to serving bowl and serve with remaining bread.