If it has hung because you dropped something conductive on it (something that conducts electricity) which has bridged some tracks on the board, then one reason for not pulling the plug, the risk of file system damage, does not apply. If that was going to happen, it happened when the Pi froze. The other reason given in the answers you linked to, which is the risk of damage to the power connector, applies if you do it lots and lots, or if you are very clumsy. If it worries you, pull the power supply out of the wall outlet.
You should not be thinking "How can I restart the hung Pi safely?". You should be thinking "How can I make 100 percent sure this never, ever, happens again?".
You are very lucky that you have not destroyed the board completely, because dropping metal things on a powered-up computer board can very easily do that. You need to get a case with a
lid, or put the board where you cannot drop things on it. You say this has happened 'several times'. You need to be more careful. Seriously.