The amount added to a lawn is like salt on steak to eat. The amount some might want to add to a one foot by two foot bin vermicomposting bin to conteract imagined acidic conditions might be like salt on a steak where the steak can no longer be seen. Worms can deal with lots of pH conditions. They can not deal with rapid change even to a "more favorable" pH. I have no scientific facts to back this up. Like you do not want to put 98 degree water onto a foot that is frostbit. The foot might of recovered but shocking it will do more damage.

I think a layer of "acidic" Starbucks coffee grounds would do more to balance yard pH than a layer of lime. I have no scientific facts to back this up.

are you using lime to neutralize acidity? if not, too much lime can affect a plant's ability to make use of NPK and other minerals. soil amendments of organic material will tend to have less drastic impact.

Yes, Slake and hydrated lime will kill your worms.