With regards to the income of manors, is 20 mythic pounds the actual cash coin that the lord receives, or is that only the case if he's able to sell off the produce?
For a lord who lives relatively near Nice (and a covenant!), is that a reasonable possibility, or will some portion of that be in the form of nonliquid produce instead?
A clarification question about vassal taxes:
Relief - in the bit where it says 'if a nobleman dies and the lord raises his heir, that heir is not required to pay relief.'
It's the value in produce (well, mostly produce anyway), most taxes were paid in kind (unless you are taxing an artisan or a merchant, they'll pay in cash). But it should be quite liquid: the lords knew what they were doing, and would not ask for something they couldn't trade off or use. Besides, what peasants produce is food, and foodstuff can always be sold in the nearest city.
Relief relates to the tax a Lord or Monarch charges to somone when they inherit anything: eg a tenant farmer dies; his son or whoever wants to take over that farm must pay the local lord some money/equivalent before he can start farming. Likewise, when a lord dies.
The details vary a lot depending on the location (and the year). In England, a large part of the King's income sometimes depended on this - he got the income from any baronies that had no lord; when the heir came of age they had to pay to be able to take ownership. If the King needed cash in a hurry, he could set the 'relief' to something affordable; if he wanted less money but over a longer time, he could set the relief at a higher level, preventing inheritance. King John found out the hard way that doing this too much leads to trouble...
The area near Nice should be more in line with Roman Law (adjusted by the Goths, then later conquerors), which is totally different! The French monarchy doesn't yet have much control (I think - been a while since I studied this), but after the Albigensian crusade gains more.
The French King did not have any control over Nice until the XIXth Century, when it was annexed to France. Until then it was under the control of other strongly independent princes, the Counts of Provence in 1220 and even after the Albigensian crusade. However the city patricians struggled with the counts over the independence of the city.