Position a rack in the center of the oven and heat the oven to 350°F.
Put the bread on a rimmed baking sheet and toss lightly with 2 Tbs. of the olive oil. Spread in an even layer and season lightly with salt. Bake until crisp and golden, 8 to 10 minutes. Set aside.
Meanwhile, in a small bowl, whisk together the garlic, vinegar, mustard, and lemon juice. Let sit for 5 minutes. Slowly whisk in 1/4 cup of the olive oil. Taste the vinaigrette with a leaf of spinach and season to taste with salt and vinegar if needed. Set aside.
Heat the remaining 1 Tbs. olive oil in a heavy-duty 12-inch skillet, preferably cast iron, over medium heat. Cook the bacon on both sides until brown and crisp, about 7 minutes. Leave the skillet on the stovetop and turn off the heat. Transfer the bacon to a paper-towel-lined plate, leaving the fat in the pan.
Put the spinach and croutons in a large bowl. Gently toss the salad with just enough of the vinaigrette to lightly coat the greens and season to taste with salt and pepper. Divide the salad among four serving plates.
Heat the bacon fat in the skillet over medium heat. Crack the eggs into the pan, season with salt and pepper, and fry sunny-side up or over-easy, 1 to 2 minutes total. Top each salad with an egg and season with salt and pepper. Tear each slice of bacon into 3 or 4 pieces and tuck them into the salads. Serve immediately and pass any remaining vinaigrette at the table.