May I inquire as to the nature of your heart disease? I am going through a MEB for heart disease as well and I took a nuclear stress test several months ago. I feel as if my condition has worsened since then, only reason I mention this is because my METS was up around 13 when I originally took the test I am not sure it would be up around that number anymore.
Have you asked your PEBLO about taking another stress test? This could be an avenue of demonstrating your condition has worsened and is deserving of a higher rating. I am not sure if you are too far along in the process to do this (I imagine the time constraint doesn't work too well with scheduling a second stress test) but it is worth a shot. Also, I was told by my PEBLO that even if I received a 0 or 10 percent rating for the valvular disease since the METS is too high - symptomatic mitral valve prolapse is grounds for an automatic 30 percent.
Now I am by no means attempting to indicate my PEBLO is the "wise man on the hill" but he has yet to give me bad information. In my case, I will find out when my results come back from Fort Sam. For you, I would recommend perhaps appealing for a FPEB, seeing if you could get a new stress test, and ensure that your connected conditions (artery blockage, etcetera) are properly documented in your medical record so there is no confusion with the decision-makers over at Fort Sam.
EDIT: After reading your response again I noticed I glanced over where you stated your related conditions were in the NARSUM. Do you have any additional documentation from a cardiologist describing these conditions? I am not sure what kind of weight supplementary evidence has with the PEB as I am new to this process like most people here. Perhaps that is something you should bring up with your PEBLO tommorow.