Having a bond wire to the gas piping is not the real issue, the appliance likely to energize the gas piping likely already performs the bonding to gas piping via the equipment grounding conductor for that appliance. The problem is CSST not being able to handle transient currents without possibility of weakening the tubing possibly causing pin holes. They don't want the tubing to carry this current, so they want to put a bonding jumper around it. Problem is they can ask us to put a #6 bonding jumper around it in hopes the tubing will not carry much current, but it is in parallel with the tubing, parallel paths will both carry equal current if equal resistance. Tubing and a #6 are probably not equal resistance but probably are not so much different that amount of current flowing in the tubing will be significantly less than what flows through the bonding jumper. IMO there is still risk of current damaging the tubing, which is what they are trying to avoid.
Water pipe clamps? - We call them water pipe clamps - in general they are for any metallic tubing or rod. If bronze with bronze or stainless bolts they often even are rated for direct burial.
Galvanized piping can not be used with natural gas, not certain about LP, but have never seen it with galvanized. Something in the gas reacts with the galvanizing. Same for copper with natural gas, LP however can be used with copper piping.