I suspect that I have angular cheilitis (have not been officially diagnosed). What causes this, so I know how to prevent it? Any home remedies?

? Vitamin deficiency. Vitamin B2 deficiency can be a cause, besides other causes as bad teeth or gum disease, ask your pharmacist about a vitamin preparation with high vit b2 content, another source is yeast tablets. If no improvement, see your dentist / primary doctor.
Angular cheilitis. Angular cheilitis can have many causes. They tend to be grouped into infectious causes, allergic causes, and nutritional deficiencies, often iron or B vitamins. You should see your doctor to get checked and find the reason for your problem. Good luck.