HI ... I'm new here and am NOT even close to being an amateur about heart disease ... HOWEVER I did have a couple of thoughts. Besides continuing to press for a definitive diagnosis through any and all testing I have some personal experience with a couple of other conditions that can mimic angina pain.
One you already mentioned ... GERD .... which quite difinitely can. I know that from personal experience as I have had it for about 7 years. The other is a hiatel hernia (sp?). My husband has this and has been rushed to the ER twice because the EMT's thought he was having a heart attack each time. He wasn't. But it DID mimic the pain .... so I'd get that checked as well. He had the pain, the sweating, the rapid pulse, bp going high .... ALL the symptoms.
Good luck with getting diagnosed! I wish my husband was like you! You carry your 'testing' into your personal life ... my hubby is a chemist and he DOESN'T! He fights every test tooth and nail even though he comes from a family smothered in engineers!!! LOL