The first paragraph is just the doctors dictation of the diagnoses that he carries (COPD, hypertension, high cholesterol, gout, arthritis, BPH) and chest pain which was resolved with nitroglycerin. The IHD means ischemic heart disease, which means there is some heart disease caused by narrowed heart arteries.
However, the second paragraph you give the 80-90 stenosis of RCA which is non-dominant. What that means is that the right coronary artery (RCA), which is the artery to the back of your heart has a 80-90% blockage, which is severe. HOWEVER, if it is non-dominant, it is a small artery that does not affect much of the heart muscle, and is something that often is not fixed with stent because the muscle affected is so small. If he actually has ischemic heart disease, and this is the only blockage, overall despite it sounding bad, is a small artery, which is reassuring. Bypass or stents to these vessels are not typically done, except in the most extreme circumstances.