It just makes me wonder how observant I really am. ... When I think back I was suspicious of the ow involved... There were a few other suspicious things but I guess I just chalked them up to grief over his dad's death.
Obviously, you were quite observant, so as to notice things that aroused your suspicions. Your observational skills are not in question.
One of the other reasons why the LBS is the last to know. Denial. Little things happen that seem off or odd but we don't want to think the worse of them, so we either accept the excuses or bury the knowledge. That's normal, it's a way not to face the pain. But it still doesn't make you an idiot.
At the moment I'm feeling a little calmer but I seem to get these sudden bursts of rage and I have to lie down for a moment until I cool off. I'm just worried that I'll accidentally interact with my H during one of these fits.
Work out a method to cool off, to think through before speaking. Whether it's 'thought control', counting to ten, or excusing yourself to go to the bathroom or whatever. That seems to work for many.