It's stretching to say that ALL government stopped. Didn't large government evolve into governments of much smaller areas?
Other than that, your answers are good.
1. Decline of centralized government-Barbarian invasions of Britain, Gaul, Italy and parts of the Eastern Roman Empire led local populations to try to protect themselves and operate independently of the central authority.
2. Decline of trade-For example, as agricultural output slowly declined and population increased, per-capita energy availability dropped. The Romans "solved" this problem by conquering their neighbours to appropriate their energy surpluses (metals, grain, slaves, etc). As a consequence of the growing Empire, the cost of maintaining communications, garrisons, civil government, etc. increased. Eventually, this cost grew so great that any new challenges such as invasions and crop failures could not be solved by the acquisition of more territory. At that point, the empire fragmented into smaller units.
3. Loss of civic virtue-the coming to an end of the participation of the average citizen in affairs of state. the perpetuation of the roman system of government depended upon its leaders to have civic virtue. Once representatives began to be corrupt and self interested the fall of the republic became imminent. At the time there was strain on the administrative system brought on by the expansion of territory under Rome's control. This corruption, when inserted into the struggle for reform, allowed for single men to take power into their own hands.
4. Economic decline-Monetary taxation was replaced with direct requisitioning, for example taking food and cattle from farmers. Individuals were forced to work at their given place of employment and remain in the same occupation. Farmers became tied to the land, as were their children, and similar demands were made on all other workers, producers, and artisans as well. Workers were organized into guilds and businesses into corporations called collegia. Both became de facto organs of the state, controlling and directing their members to work and produce for the state. In the countryside people attached themselves to the estates of the wealthy in order to gain some protection from state officials and tax collectors. These estates, the beginning of the feudal system, operated as much as possible as closed systems, providing for all their own needs and not engaging in trade at all.