Ben---
It depends on the size of the Knight's holdings of land and his rank. An earl or baron would have a squadron of knights, a knights might have a bully boy or two. They might be in charge of local justice and were given the title Shire Reeve. This comes from the title gerefa, or "high official" in Middle English, because he led a ROF ("several soldiers").
These words then allided and changed to form "Sheriff".
So -- the sheriff of Nottingham had his "several soldiers" but your average knight probably was lucky to have a squire (aged about 10).
Militia is a modern word to describe something much less formal back then. If a band of robbers or raiders struck a village, villagers might run around with whatever "weapons" came to hand -- pitchforks, staves, clubs, cudgels, knives. they would usually act defensively, eg trying to get the women and children into a safe place, such as a church (one of the few solid stone buildings, probably).
Ironically, such improvised weapons led to the development of a superior infantry weapon, and variants, such as the bill hook. These were sometimes called halberds, although these often lacked hooks.
A simple scythe, mounted on a long pole, is ideal for "hooking" a knight and pulling them off their horse. a knight in armour on the ground would struggle to get up -- they were like turtles turned on their backs. So -- crash -- knight down -- stab stab stab -- this is an ex knight, pushing up the daisies.
If a knight had a retinue of soldiers, they would eat near the top table, near the fire. Status was measured by how far from the fire you were and whether you go meat cuts or scraps.
Few households had regular guards on permanent watch -- this is why homes had dogs or, still used in Scottish disilleries, geese.
What kept the peasants under control? Not just brute force, although that happened. The church preached acceptance -- that everyone accept their station in life and not try to change or rise above it. Fathers and mothers taught their children their trades. Nothing changed. The church preached rewards in the afterlife. Today we want our rewards NOW.
Hope that helps.