My opinion only. Not a doctor! Take with a handful of salt.
The only thing you mentioned that changed dramatically was your diet. Therefore, from Occam's razor which says that the simplest answer usually being the best, look at the diet as the culprit. Adding a bunch of honey aka fructose, is like drinking a lot of sodas, so that could be doing something too.
I'd see an allergist and make up a list of all the foods you ate while on the diet, also all medicines, everything you drank and don't forget the honey.
You sound like what happened to me a couple of days ago when I accidentally ate some cereal with my food trigger. I didn't check the ingredients on the package carefully enough and consumed molasses, which contains sulfite. I felt miserable, tired, heart racing, hard to breathe. After a while I had nausea and diarrhea. The last symptom was because I ingested a fairly high dose of sulfite, a large bowl of the cereal. What made me mad was the labeling on the package promising all natural, gluten-free, no preservatives. Sulfur dioxide is added to molasses as a preservative!
What's in that Rice Protein? Rice doesn't have much protein. What was added for flavor? According to Doctor Wikipedia, Rice protein is high in the sulfur-containing amino acids. I sure won't be trying it! I'd be in the ER for sure!! I'm intolerant to sulfites to the degree that once I had a heart attack triggered by eating cereal with dried fruit (heavily sulfited).
Just my personal opinion and experiences. You could have something totally different! My allergist helped me find my food trigger. Weeks before my heart attack I was tested up one side and down the other for chest pain and tachycardia and was told I was "just out of shape."
The reaction is not unknown. It's called cardio-esophageal reflex. There are many papers you can google. The heart is connected to the gut, stomach, many other organs by the vagus nerve. So when one part gets irritated another part can react. When I eat my allergen my stomach and esophagus become irritated and the heart responds.
I'll bet the white patch and the itchy ears were something else altogether, not related to the racing heart.
Look in the search box at the top of the page for food journal, trigger foods, and you'll find many posts on this subject.
But, remember, this is a forum, not a doctor's office and I could be WAY out in the ozone. Just a patient.