Dull ache directly below middle of ribcage. cardiovascular issues ruled out. hiatal herni?, ulcer? gerd? thoughts?

Yes possible : Hiatal hernia and/or gerd high on list of possibilities. Peptic ulcer, gastritis also quite possible. Gastric or pancreatic cancer less likely but as age > 40 become possible though not likely. A 10-14 day trial of acid blocking medication like otc Prilosec would be reasonable but seeing gastroenterologist for consult suggested, .