What's the actual number range for total value of all clan's fiefs?
The value of fiefs typically fall within the range of about 300,000 in the case of lower end castles to 5,000,000 in the case of high end towns. There are a variety of factors that affect the value of a fief, but you can get a rough approximation of their value with the following equations:
Towns:
750,000 + (Prosperity x 1000)
Castles:
250,000 + (Prosperity x 1000)
Villages:
100,000 + (Hearths x 250)
Since villages are always bound to either towns or castles, you need to add the value of each the villages to the value of their bound settlements to get the total value of the fief. At the end, multiply the total value by 0.33.
So for example, if you have a town with 4000 prosperity and 3 bound villages with 300 hearth each, its value will roughly be equal to [750,000 + (4000 x 1000)] + [100,000 + (300 x 250)] + [100,000 + (300 x 250)] + [100,000 + (300 x 250)] = 5,275,000 x 0.33 =
1,740,750.
As a comparison, a castle with 1000 prosperity and 2 bound villages of 300 hearths each would have a value of roughly
528,000.
With merit score, the game is basically trying to distribute the value of fiefs to clans according to their rank. Tier 5 clans should have more total value in fiefs than tier 4 clans, who should have more value than tier 3 clans, etc. If the fiefs a particular clan owns are less valuable than they should have for their rank, then their merit score will be higher and they will have a good chance to appear on the ballot and earn a fief. If a clan has a lot of strong troops or conquers a fief themselves, then their merit score will get a boost, potentially allowing them to have more valuable fiefs than they otherwise would for their clan rank. The merit score is pretty favorable to the player, but that still doesn't mean that they will get to keep all of the fiefs they conquer.
Currently, I don't think there's a legit way for you to keep all of the towns for yourself as a ruler (besides only having 2 vassals), but if it's for the sake of roleplaying, you could always just use the console command "campaign.give_settlement_to_player" to give yourself all of the towns and leave the castles for your vassals.