A dermatologist's exam is much more reliable than anything I can say. Before I even get to your questions, it is unlikely you have herpes or that it explains your symptoims (which I haven't read yet).
Now I have read the next statement. It was wrong of you to insist on treatment for a condition that your doctor didn't think you had, and anyway, if you had oral herpes with symptoms that had been going on more than a couple of days, treatment wouldn't help. If you had seen me, I would have refused your request for a prescription for acyclovir.
OK, now I have read everything. The fact that the bump didn't change on acyclovir proves it wasn't herpes, and it sounds like the blood test confirms that conclusion. To your specific questions.
1) Irrelevant. You don't have oral herpes.
2) No, herpes cannot behave that way. You should have listened to the dermatologist.
3,4) I haven't a clue what it might be. Since it is so hard to even notice, it's probably some sort of normal anatomic variation, like a promiment mucus-secreting gland. It doesn't sound to me like an oral hygiene problem, but my expertise is limited to STDs.
I suggest putting herpes out of your mind, then follow up with the dermatologist if you remain concerned. Or visit your dentist to deal with both this question and the oral hygiene issue. If either of these providers believes nothing is wrong, you can rely on that judgment.
Good luck-- HHH, MD