ok, I have crunched some numbers and here are some of the results -- giving a basic overview of what I am thinking will be in this town....
Garrison - 1 (4 buildings, 400 soldiers -- that is 2 companies, and a HQ detachment)
Innkeepers - 2 (15 people)
Taverns - 3 (20 people)
Clothiers - 2 (15 people)
Apothecary - 1 (5 people)
Physician - 2 (10 people)
Leather Worker - 3 (20 people)
Weapon Crafter - 2 (20 people)
Wood Crafter - 3 (45 people in total)
Blacksmith - 3 (20 people)
Chandler - 2 (10 people)
Ostlers - 2 (20 people)
Customs - 1 (15 people)
Miller - 2 (10 people)
Mason - 2 (20 people)
Courtesans - 3 (80 people)
Lexographer - 1 (5 people)
Embalmer - 1 (5 people)
Thieve's Guild - 1 (30 people)
Locksmith - 1 (5 people)
Potter - 2 (15 people)
Jeweler - 1 (10 people)
City Hall - 1 (30 people)
Town Guard - 1 (90 people)
Guild Hall - 1 (10 people)
Mage Guild - 1 (10 people)
Miscellaneous - ?? (85 people)
Total ~1,000 permanent inhabitants...
(exlcuding traders, caravans, adventurers, etc..
The Wall is going to be about 15' thick, and 30' high. It is a total of approximately 7 miles in length, and will have one tower (50' high) at each end, and then another tower about every mile along its length.
There is 1 tower just north of the river, and the town will be just south of the river, with the gate through the (the gatehouse is 20' wide, 30' high, and 50' long) about half a mile south of that tower (and about half a mile north of the next one).
Each tower will be manned by 2 squads (half a platoon), putting a company of troops into the towers at any given time. Each platoon spends 2 weeks in their towers before they are relieved. Upon returning to the barracks, they spend 2 weeks manning the gate, and then stand down to barracks duty/training, until their turn to go back out to a tower.
This results in 3 platoons being ready to be used to reinforce any tower that needs it, and no tower is more than 3-4 miles from the garrison, making it easy to send for those re-inforcements when needed.
The biggest danger to the garrisons, are the large predators outside the walls (i.e. carnivorous dinosaurs). that occasionally think that there is more food on the garrison's side of the wall....
Among the villagers, not only are there folks from the colony who are heading out for adventure, but there is also the occasional trader, including some Orc traders who come from their lands every once in a while (and yes, the Orcs visit the brothels as well -- this being the primary source of any half-orc characters...). Think of orcs as having personalities similar to how Klingons are depicted in Star Trek. They are a warrior race proud and fierce, but not inherently evil -- although they ARE extremely territorial, and if you enter their lands without permission, your life is forfeit if they catch you. Outside of their territory (and they have good lands, so have no interest in expanding), they will be brash, loud, and perhaps a bit mouthy, but they do not go looking for fights (at least not if you haven't insulted them -- and they have learned the etiquette of bar brawls (no killing)).