2 questions - muscle groups & lifting to failure

Is it worth doing specific muscle group workouts if you are only going to the gym 3 times a week? I.e. I have this workout plan which is is broken into: Shoulders/Traps Back/Biceps/Forearms Chest/Triceps Legs

Each category has a light and heavy day workout.

But if I am going 3 times a week, one muscle group won’t even get a workout and there’s about 8-10 days between each muscle group workout alternating from light and heavy.

Second question, how often should I be lifting to failure? I don’t have anyone spotting me so it if I do, I’m in a real pickle if I can’t get back up so I don’t feel I am challenging myself if not…