Zoraster was a descendant of Abraham... I'm not sure if he grew up as a member of an Abrahamic religion however.
Anyways. So no one has a comment about "providers" only need take up 1/3 of a covenants population to be "self sufficient" under Covenant's RAW?
If you remove taxes and have a good situation overall, 1/3 isnt unreasonable.
It will be vulnerable though as it doesnt really leave any real margins for bad harvests or injured workers or other "events".
Of course, that can be handled as part of stories and stuff, and then it becomes quite fine.
It depends on how you run the place...
Whoops, wish I'd read this before talking smack about Buddhism in the other thread I tried to steer the discussion into.
I have to admit that's way out of line with standard demographics. I'd suggest reducing the value craftsmen have towards lowering provisions costs, but once you get around to trying to decide on the right numbers, you're researching medieval demographics yourself and don't need rules to decide how many people your covenant should have.
Ah... Whatever. At this point, I don't want to do that kind of research.
Three times in one day I've gone over something I know I've looked at several times and find something completely new.
Google this time brings me this: welshpiper.com/medieval-demographics-online/
I picked the most fertile land the tool supports, as you will have magical assistance.
It suggests that, for a 3 square mile parcel of land (the smallest parcel you can have without the formula for arable land shorting you), you will have a single large village (itself occupying 0.38 square miles, the rest being devoted to agriculture of some sort) of around 360 people.
The population breakdown for your large village is a "Ruling house" of indeterminate size (it's randomized), but easily more than the number of magi and companions combined. Setting it to "tyrannical" law enforcement (the law enforcement will be doubling as shield grogs), there are 15 people holding administrative duties. After that there are 20 more people that could be labeled "craftsmen." The other 300ish people will be farmers, herders, families of the listed craftsmen...
rpglibrary.org/utils/meddemog/ is the one I checked before, but I guess I didn't read every line closely enough, because originally it looked like something that wasn't useful. It's supposedly based on the same math as the previous, but presents it differently. It adds on that you will have 538 fowl (e.g. chickens, geese, ducks) and 254 dairy and meat animals (e.g. cows, goats, pigs, sheep). I don't know how many people have to be devoted to husbandry to cover that many animals, so the exact farmer/herder ratio remains undetermined. Also, it presents the craftsmen fractionally, and it's obvious that there are room for full craftsmen occupying two or three roles. For example, 0.65 carpenters + 0.51 coopers is definitely an additional "woodworking" craftsman. Still, the impact isn't going to be large compared to the 300 peasants you have wandering around.
For truly long term survivability, you will need at least 2 of any craftsmen you desire: A master, and an apprentice. However, apprentices are built in to the demographics, so your total number of covenfolk will still be around 360, it's just more of them are craftsmen than the numbers first suggest.
Thanks for posting those links and the results!
Remember that labourers can only hit 50% of the provisions costs, and you are capped at a saving of 20% per craft so you'd need 3 appropriate craft skills along with enough trained people to get the saving to 100%.
And then of course the labourers and craftsmen that you have gotten add to your costs so you need more labourers and craftsmen to cover for them as well 
I've got a spreadsheet hanging around that has the Covenants book stuff in a spreadsheet that was used to run the finances for a 150 year campaign, the maths is involved.
I already did a spreadsheet, thanks though.
Best ressource ever!