--- The term my ENT used was that the node had "stable structure".
Great, that includes having the hilum. (Cancer effaces the normal structure.) Do you have the sono report? If not, you really should get it especially because you might want it years from now. Knowing both dimensions would be helpful, especially if it's very long and thin which is okay to have. Round is bad.
--- I also have inappropriate sinus tachycardia
Aha, do you work in the medical field?
--- and at times my parasympathetic nervous system is very over-reactive
I'm not sure what you mean there. Since parasympathetic is the relaxing side, as opposed to sympathetic which is the stimulatory side.
--- so I am hoping this is another over-reactive type thing.
Your reaction (on your other thread) to the FNA needle is illuminating. Possibly over reactive mast cells. Can you draw a line on your sternum with your fingernail? Do you flush easily?
Hi, I'd only be alarmed if it started growing again or if others started popping up in other regions.
"...seems to coincide with my allergies and sinus issues"
I think you're correct in thinking that this is all based in your immune system, which is possibly over reactive.
Do you have an Fx of odd immune conditions?
You can look up 'granuloma' as the likely reason that the one node has not gone down.
It's unfortunate that your sono report apparently did not mention the presence or absence of the hilum in the big node. Or did it? The hilum being seen would be very reassuring of not-cancer.