Proper GND pours for two-layer PCBs?
It's a common design strategy to have a GND copper pour, which covers most of the bottom copper layer.  In this strategy, the bottom layer is used for routing as little as practical in order to keep the GND copper pour uninterrupted.  The goal is to mimic a ground plane like in a 4-layer board.

Here's an example: 

Let's see how this would agree with the design rules in the O.P.  I treat them as general rules.  I'm ignoring more specific things, such as low noise circuits or power circuits, which may require a different interpretation of these rules.


A ground plane is under the signal trace.  The DC component of the return current follows the path of least resistance.  The AC component of the return current follows the path of least impedance, and it runs under the signal trace.
Star ground.  Each sub-circuit can sit on its own local GND copper pour.  Local GND pours are connected to one point, which will be the center of the star.  Alternatively, slits can be made in the GND pour between the sub-circuits.
Minimize the return path length may conflict with rule 1.  Which would it be: minimal path or same as the signal?
Ground connection should have low impedance.  Usually, ground traces are wider than signal traces.  I doubt that "same trace width as the signal" is a good rule for the general case.


Design rules similar to the ones in the O.P. are also discussed here and here.  (Analog devices has quite a few application notes on grounding.  Search their site.)