Add the olive oil, lemon juice, minced garlic, dried Italian seasoning, sea salt, and black pepper for the chicken to a medium bowl and whisk to combine into a marinade.
Place the chicken breasts in a shallow dish or zip top bag, pour the marinade over them, and turn to coat all sides evenly.
Let the chicken marinate in the refrigerator for at least 30 minutes and up to 2 hours, then remove it and allow it to sit at room temperature for about 15 minutes before grilling.
Preheat a grill or grill pan over medium to medium high heat and lightly oil the grates if needed to prevent sticking.
Grill the marinated chicken breasts for about 6 to 8 minutes per side, or until they reach an internal temperature of 165°F, then transfer them to a plate and let rest for at least 5 minutes before slicing.
While the chicken cooks, cook the bacon in a skillet over medium heat until crisp, then transfer to a paper towel lined plate to cool before crumbling.
In the same or a clean dry skillet, toast the sliced almonds, pumpkin seeds, and sunflower seeds over medium low heat, stirring frequently, until fragrant and lightly golden, then remove from heat and let cool.
Make the dressing by adding the mayonnaise, olive oil, minced anchovies, Dijon mustard, lemon juice, minced garlic, grated Parmesan, Worcestershire sauce, sea salt, and black pepper to a mixing bowl.
Whisk the dressing ingredients together until smooth and creamy, then taste and adjust salt, pepper, or lemon juice to your preference, thinning with a splash of water if desired for a looser consistency.
Prepare the romaine by removing any wilted outer leaves, coring, and chopping into bite size pieces, or by halving the heads lengthwise if you plan to grill them.
If lightly grilling the romaine, brush the cut sides with olive oil, place them cut side down on the hot grill for about 10 to 20 seconds until lightly charred, then remove and chop once cool enough to handle.
Add the chopped romaine to a large serving bowl and drizzle with a modest amount of the Caesar dressing, then toss gently to coat, adding more dressing as needed to lightly but thoroughly dress the leaves without making them soggy.
Slice the rested grilled chicken breasts into strips or bite size pieces and arrange them over the dressed romaine.
Top the salad with shaved or shredded Parmesan, crumbled bacon, toasted almonds, pumpkin seeds, and sunflower seeds, reserving some of each for passing at the table if desired.
Serve the grilled keto chicken Caesar salad immediately with extra dressing, lemon wedges, and additional Parmesan on the side for anyone who wants more.