Welcome to the forum, bear.
If the docs didn't find any research, they didn't look for it. Cardioesophageal reflex, aka linked angina doesn't have a lot of papers, but they are available. One paper described how the reflux can trigger coronary vasospasms, which can cause a plaque rupture, which becomes a heart attack.
My triggers are foods, drinks and medicines. My allergist had me keep a good food journal, writing down what I ate drank and meds, with times and reactions, especially within 2 hours. People who react with migraines can react as much as 2 days after consuming a trigger. If you do a search in the box at the top of the page, you will find a large number of posts on this subject.
I react to pork, gelatin, wine and beer, corn starch, maple syrup, onions, and a lot of prepared frozen, dried and deli foods. On getting together my list I googled some of them with the term "food allergies." I came up with a connection - sulfites. You may have a very different trigger. It takes a couple of months at least to get a good list.
Tinnitus may be from something else altogether. I get it from my cholesterol med.
Cutting down on foods with even medium amounts of sulfite minimized my reflux. My stomach doesn't react quite so much since I needed the surgery for it, but I still get bouts of tachycardia and arrhythmias if I go over my daily limit for sulfites. I can usually get relief from an attack by doing "valsalva maneuvers." If that doesn't work I take a beta blocker. Propranolol works fast but not long. I've gotten a little worse lately, so I'm on a half the smallest dose of atenolol daily. That's cut the number of attacks for me.