This is kind of a silly question but one that I couldn't find a definitive answer on. I'd like to use a typical faucet flex hose (3/8 compression to 1/2 FIP in this case) to connect to a brass 1/2-NPT male nipple. Most of the flex lines I find labelled for 1/2 FIP use a conical rubber washer. Will these properly seal against a male NPT that doesn't have a pronounced inverted taper (on inside of pipe)? What makes me suspicious is that I remember an old Kohler faucet I installed many years back included 3/8 compression-to-1/2" FIP adapters for use connecting to old MIP stop valves, and these washers were FLAT, not conical. Does it matter? I know either way the threads don't do the sealing, but can these FIP connections be used on both taper and straight pipe threads (with and without a pronounced inside taper?) Thanks for reading!

There is a 2" gas pipe that runs throughout the 3 floors of our house. The house used to have gas lighting in every room, so that explains why the gas line is so big. The gas has been off for years now and we want to remodel but need to cut out these old pipes. The line is capped so there's no way to release any gas that might be inside. So, how can I cut this safely given that a sawzall throws sparks?