Hi RPG Weirdo, thanks for joining the ACKS community.
One of the biggest complaints about the ACKS Core Rules is that I didn’t spend enough time explaining how the advice in the Secrets chapter was supposed to be implemented in light of the game mechanics in the Campaigns chapter.
To answer your question: Your math is correct, but one of your assumption is wrong. That is, the levels listed on the Demographics of Levelled Characters are emphatically NOT the maximum levels that a lord might have! " The Demographics of Leveled Characters table just shows “the approximate frequency of leveled characters per person and the likely realm such a character might control.”
Simply from ruling for a period of years, a lord can and will rise to about one level higher than the level listed. (As you noted.) And any lord could go adventure tomorrow and gain levels and become as powerful as a king, if he was willing to take the risk. As such, it’s possible that the local baron with a 500gp-realm is actually 7th level or 11th level or even 14th level.
Conversely, the levels listed are NOT minimums either. It’s entirely possible that the king is only 1st level, having just taken the throne.
So if they levels listed aren’t minimums and aren’t maximums, what are they for? They’re intended as guidelines for a GM building his first ACKS setting. By design, they recommend lords that are about one level below the maximum possible. That way, the campaign begins with the rulers that are a bit “uneasy in their thrones”. This has the beneficial side effect of making it easier for them to be toppled by adventurers as they move into the campaign tier.
Given the economics of their realms, mathematically barons will eventually level from about 3rd to 5th level, marquis from 5th to 7th level, counts from 7th to 9th level, dukes from 8th to 10th level, princes from 10th to 12th level, kings from 11th to 13th level, and emperors from 13th level to 14th level. Notice that at each rank, the most powerful of the lower title are about on par with the weakest of the next title. This “overlap” is important and deliberate, as its what makes it viable for a duke to unseat a prince, and so on, in the “conquest” portion of the game.
That is, the system is deliberately set up to fuel the ambitions of a ruler, because given enough time every ruler ends up needing a bigger realm to advance, and there aren’t enough such realms. In fact, if you want to set up a realm where the nobles are about to go to war with each other, then put them all at max level and scheming to conquer each other!
In terms of how fast NPCs level, remember that most NPC lords are henchmen of more powerful lords, so they earn only half the XP of a PC. This dramatically slows down leveling. A 0 level character will take about 11 years to reach 5th level if he inherits a barony.
I hope that answers your question. If you’re the sort who enjoys delving into the math and economics of RPG domain level play, I highly recommend you join the Autarch Patreon and check out the various new rules that have been provided there, as we go much, much, much MUCH more in depth there, down to detailing the farms, average ages of nobles, etc. Our Discord also has a lot of, uh, lively Q&A.