Stephanie, I am sorry Bailey is not feeling well, I am sure you must be worried. In response to your question, when we see diarrhea with streaks of blood this is a sign of inflammation in the colon (large intestines). This is not related to the chocolate he ate on Friday, the chocolate should not be an issue by now. The odor in the ears is not related either. It will be difficult for me to determine the exact underlying cause without a hands-on examination and some testing. But, common causes are dietary indiscretion, ingestion of a foreign body, infections, parasites, etc. to name a few causes. Unfortunately, on history only it will be difficult to determine the exact underlying cause, I am sorry. In this case, I would recommend a hands-on examination with your family veterinarian and a fecal analysis as an initial screening test. In the meantime, this is what you can do:
1- Do not give things like Pepto Bismol or Imodium. You see, stopping diarrhea with medication can make things worst if this is related to an infection or ingestion of a foreign body.
2- No food or water for 6-8 hours, need to give his gastrointestinal tract time to rest. Then, offer a small amount of water followed by a diet of rice (75%) and boiled boneless chicken or ground beef (25%) until the stool is back to normal then wean him back into his regular diet. Keep him indoors in a cool room and no exercise when fasting.
3- Supplement with a probiotic, these are friendly bacteria that help with regularity and inflammation. You can buy this over the counter in any pet store.
4- Follow up with your family veterinarian for a hands on examination. If cost is a concern look into your local ASPCA or Shelter where they often offer veterinary services at a lower cost.
My goal is to provide you with excellent service - I hope I've provided the information you were seeking, if you feel you have received anything less, please reply back as I am happy to address follow-up questions. Kindly rate me when you are done.