if the cardiologist wasn't worried there is ABSOLUTELY no reason for you to even give it another thought. Especially to be diagnosing yourself with pots. I have sinus tachycardia (my heart rate is always over 100bpm and there's no explanation for why) and have for years, and I'm completely fine. I've been through all sorts of tests to try and figure out why even though I wasn't really uncomfortable. They wanted to see if it MIGHT be something dangerous. If something is weird, doctors will investigate to try to find the cause for why its weird.
They know what is normal and what isn't - they don't use google for their diagnosis, they use their actual clinical experience which they have earned from years of internship, medical school etc. On top of that they have done YEARS off extra study to specialise in their field, and would notice something as obvious as that without question. :)
they absolutely know the danger signs in people of all ages and stages of illness, not just from study, but from having treated them, and they Know what to LOOK for. All sorts of signs that to the untrained eye (like us) seem unrelated, but that they can make sense of through their experience of having seen it before.
I'm not a doctor, but I imagine the blood pressure on one side of your body being higher would kind of make sense anyway as your heart is further to one side than the other anyway.
In other words, if your cardiologist didn't think it was anything to worry about, your fine. :) if you had any worrying signs at all they would have sent you for further tests etc. it's not worth their career to ignore something dangerous, or even something that has the potential to be dangerous.
It would probably be best to put the blood pressure monitor and the old reports away though, those things are definitely not going to help you health anxiety...