How do Humility and Mishra's Factory interact?
If you activate Mishra's Factory's second ability while Humility is on the battlefield, Mishra's Factory will be a 2/2 Artifact Creature Land--Assembly-Worker with no abilities for the rest of the turn. If you activate Mishra's Factory's second ability, then Humility enters the battlefield later in the turn, Mishra's Factory will be a 1/1 Artifact Creature Land--Assembly-Worker with no abilities for the rest of the turn.
Mishra's Factory's second ability has this text:

{1}: Mishra's Factory becomes a 2/2 Assembly-Worker artifact creature until end of turn. It's still a land.

Upon resolving, this ability creates a continuous effect that lasts for the rest of the turn and exists independent of the Factory's current characteristics.
and Humility has this text:

All creatures lose all abilities and have base power and toughness 1/1.

This is a static ability that creates a continuous effect that always applies as long as Humility is on the battlefield.
As mentioned in the question, both of these effects apply in layers. Mishra's Factory's effect adds the Creature and Artifact types and Assembly-Worker subtype in layer 4 and sets the power and toughness to 2/2 in layer 7b. Humility's effect removes the creature's abilities in layer 6 and sets the power and toughness to 1/1 in layer 7b.
These modifications are applied in order by layer. So, first Mishra's Factory gains the Artifact and Creature types and Assembly-Worker subtype in layer 4. Then, because it is now a creature, Humility removes its abilities in layer 6. Then both effects try to set the power and toughness in layer 7b. At this point, the timestamp rules come into effect:

613.6. Within a layer or sublayer, determining which order effects are applied in is usually done using a timestamp system. An effect with an earlier timestamp is applied before an effect with a later timestamp.

613.6a A continuous effect generated by a static ability has the same timestamp as the object the static ability is on, or the timestamp of the effect that created the ability, whichever is later.

613.6b A continuous effect generated by the resolution of a spell or ability receives a timestamp at the time it’s created.

613.6c An object receives a timestamp at the time it enters a zone.



So, the timestamp of Humility's effect depends on when it entered the battlefield, and the timestamp of Mishra's Factory's effect depends on when the ability resolved. Whichever one is later overrides the earlier one, so if Humility entered the battlefield second, the creature will be a 1/1, and if the Factory's ability resolved second, the creature will be a 2/2.