I'm not sure I understand your question. Are there any concerns with protein-dominant meals? Not if your protein sources are of good quality (Primal). How much plant matter is enough? That's going to vary by individual and from day to day.
Try not to get locked in to 3 meals and 1 snack. Sometimes I'll do lunch and dinner, no breakfast, no snack. Or breakfast and dinner. Intermittent fasts are fine, and the idea is to eat when hungry.
Don't worry about getting enough fiber. If you want to incorporate more plants into your diet, eat seasonally and just keep trying out new recipes.
I've done LC/VLC sporadically, but not strictly. Some folks have success with it and others not. When I first went Primal, I went VLC during the week, and let loose on carbs on weekends. Worked for me.
When you're eating quality foods and lose the taste for sugar, grains, fast food, and processed food, you will naturally fall into a healthful eating pattern that's right for you and what your body tolerates. Don't force a rigid, structured "must eat 10 servings of vegetables per day" kind of thing on yourself.