That is not how it works because it is still considered an attack and it places damage counters and if a pokemon would be knocked out by silent fear the effect of Bisharp would still happen so 30+60=90x2=180 for a single energy. Wow that bisharp just made trev break less viable because that retailiate will easily knock out a trevanant. Having resistance will also help a lot as well. Can also do a big chunk to fairy pokemon doing the x2 weakness then -20 after still a solid attack.
False. Bisharp says "If any of your Pokemon were knocked out by DAMAGE from an opponent's attack..."
Silent Fear doesn't do damage, it places damage counters, so if it KO's anything it doesn't count as them being knocked out by damage, but instead as being knocked out by an effect of an attack.
Trevenant Break is just as viable as before, so calm down there. Bisharp being a stage one is a lot more hindering to its inclusion in a deck than it being a basic would have been, so this card will only be run in decks that have space for it and desperately need a way to counter Trevenant.