I think the heartbeat issue is related to having such low blood pressure and your heart having to work significantly harder to pump blood through your body. Are you anemic?
The burning in your stomach sounds reminiscent of ulcers. I’m hardly an expert ( I don’t even have EDS, but I’m taking care of someone who has it). Perhaps try removing gluten, dairy, soy, eggs from your diet. Do this for at least a month.
Try eating these:
If you get nausea, try limiting your fat intake. If it helps, continue eating low fat. Otherwise, continue eating fat as it can be easy on the body (especially medium chain fatty acids like those in coconut oil).
Do you poop regularly? How frequently do you poop? It seems like an awkward question, but it helps in determining how quickly your stomach is processing food. Gastroparesis is not uncommon in those with EDS.
How frequently do you pee? Another awkward question, but if you pee a lot, your body is losing vital salt that it needs to help maintain blood pressure.
My guy (with EDS-hypermobility) has a fast heart rate and chest pain, much like you describe. We haven’t yet been able to attribute it to anything other than his POTS. You most likely have POTS. Dr. Diana mentioned a combination of zyrtec and zantac in dealing with POTS. Staying hydrated and eating salt helps with the blood pressure, since salt helps the body retain water and thus increases blood pressure.
Be very careful about operations. People with EDS often have a lot of complications with operations. Try to explore every possible option before an operation.
Welcome to the terrifying world of EDS, were you must learn everything you can about your illness, because most doctors won’t know anything. That being said, the internet is an amazing tool. Make use of Dr. Diana’s posts and the discussions on Inspire.