This is not a full answer, but answers some of your points. From a 2015 International Code Council article on "bonding of corrugated stainless steel tubing (CSST) piping system "
Why bond? Because potential differences can cause arcing to and then holes in the thin-walled CSST:
The bonding of CSST piping
system to the grounding electrode system of the structure in
which the CSST is installed will lower the voltage build-up on
the CSST caused by unintentional energizing from outside
sources such as power surges and lightning strikes. The
bonding will help achieve an equi-potential state between the
CSST and other similarly bonded metallic systems (such as
the water piping, structural steel, electrical raceways and coax
cable). The bonding will help reduce the possibility and severity
of arcing between these conductive systems when energized by
a lightning strike on or nearby the premises.
The point is to equalize potential among the various metal systems, not necessarily to have the CSST match ground potential.
Thus, "A separate grounding electrode
and grounding system cannot be established just for the fuel
gas piping system" (your headline question)
Clamp/bond requirements:
- "The bonding clamp can
be located at any location within the piping system. "
- "The bonding conductor must be not longer than 75 feet "
- "The corrugated stainless steel tubing itself must never be used as a
point of attachment of the bonding clamp."
- "The clamp can be attached to a length of rigid pipe, a malleable
iron pipe fitting, a prefabricated manifold, or a brass CSST
fitting."
- "The bonding clamp must
be accessible and can be located outdoors or indoors."
- "Only a single point of attachment is required regardless of the
length or complexity of the piping system. "
Now, if your gas line is connected to an appliance that also has an electrical connection, it will likely thus be indirectly connected to the appliance's equipment grounding conductor. Such a connection won't meet the requirements above, but in practice it may suffice to give most or all of the anti-arcing benefit.