1- You have to level up your character and spend a lot of points in charisma and leadership to have a bigger army, also you will need to gain renown which will grant you additionnal troop slot. There is mercenaries available in taverns, militians also can be upgraded into mercenary infantry of higher quality.
2- AI formations work just fine, if you fought outlaws then don't be surprised, outlaw parties are NOT using formations no mater the option you set in pbod. Faction armies will use formations and spcial orders if you enabled it.
3- It's a weapon, just buy one from a marketplace and you'll be able to outfit yourself as one of your soldiers, every faction soldiers uniforms are available in marketplace based on faction owner of cities (at game start).
4- Have you recruited troops from british village instead ? If you used the british starting armies it will have issues such as reseting the map to native names etc, and it's not fully working anyways. Recruit troops from village of the faction you want to fight for and it will be fine.
Hope this helps, also can you please add, when asking for info/help, if you are playing on the 1812 Beta II or the Beta III ? It make it easier for me to answer correctly, cause there's some differences between the two, and not just uniforms models ...