Proper bedtime is by far the most important and deserves the 100% mark. Missing out on deep sleep before midnight negatively affects the digestion of food, elimination of waste, the immune sytem, mental functions, emotions, and the amount of energy each cell requires for its trillions of chemcial reactions per second. With tiredness, regardless whether you stimulate the body or not with nicotine, caffeine, meat, TV or other things, the body has to struggle to perform, and you will get stressed. I have discussed this effect in greater detail in my books It's Time to Wake Up and The Key to Health and Rejuvenation, ener-chi.com.
Emotional health and eating habits combined may exer the second most important influence on your health. You can neither really separate the two, nor put a percentage tag on them. Your choice of food largely reflects how you feel about yourself and the world. You unconsciously desire foods that harm you if you feel guilty about something you have done or said, even it was years or lifetimes ago. Usually, comfort foods serve as means of self-punishment, unconscious that is. If you trully accept and love yourself, regardless of your flaws, your natural instincts will guide you in your choices of food, lifestyle, exercise and relationships. These will mirror that caring, loving relationship you have with yourself. See more details about this in my book Freedom from Judgment, ener-chi.com).
Eating your main meal of the day in the evening instead of noontime play a huge rule in causing food cravings, putting on extra weight (waste), developing all sort of gastro-intestinal trouble, and becoming sluggish and depressed (more about this in The Key to Health and Rejuveantion).
Exercise is very important for both the body and mind. I would give it a 60%-80% importance, depending on whether you use you body physically or live a very sedentary lifestyle. Not moving congests the lymphatic system, thus affecting the health of every cell of the body (see more info about this on my website www.ener-chi.com).
Whether alcohol is harmful to you depends a largely on how well your liver is able to break it down, how much water you drink to prevent the alcohol's dehydrating effects, how often you drink and how much you drink at a time. If you drink a lot, it may affect your body even more than sleep deprivation does. So I rather not put the percentage tag on this one either.
I would say, let your body be the guide in what you want to tackle first. I would say, proper bedimes.